Get in touch with technology with tech Stuff from how stuff Works dot com. Hey there, and welcome to tech Stuff. I am your host, Jonathan Strickland. I'm an executive producer with how Stuff Works in I love all things tech, though today we're gonna be talking about a branch of technology that gets up. I'm pretty grim and pretty serious. Uh, this is a listener request. Listener Hakim asked that I do an episode about forensic technology, so I'm actually gonna do a pair of episodes. It is fascinating stuff and it's definitely not quite the same as what we see in depictions on film or in television shows. That's not a big surprise. We've covered multiple times how technology in pop culture is very different from what we see in reality. But in this episode, I'm going to specifically focus on the history of forensics, and in the next episode we'll talk about some of the cutting edge technologies that are used in for psick investigations today. So forensics, first of all, has a few different definitions. If you are being very literal, it can mean debate or discussion in Latin, but as we tend to use it today, we refer to it as the science with regard to detecting and solving crimes. So not just if a crime has occurred, but how did a crime occur, how did it unfold in time, who was involved? That sort of stuff. And like all sciences, forensics can trace its history back far before the formal codification of the scientific method, and this involves lots of different ideas and processes for different elements of investigation developing at various times throughout history. Like most things, forensics involved a lot of different ideas being tested throughout centuries before maturing as a collection of practices. So one of the easy ideas we can talk about, because there are a lot of different independent threads that converge to become forensics. On easy entry point is a discussion about fingerprints and developing the skills and technology to detect and identify them and classify them in the context of criminal investigations. Now, I've done a full episode on fingerprinting in the past, so I'll give more of a short overview of the whole thing here. There are records that actually indicate that handprints were used as evidence and investigations for burglary back in China more than two thousand years ago, and the book with the English title Universal History, which was published in Persia in the th hundreds, mentioned the practice of identifying people based upon their fingerprints. European anatomists and philosophers made observations about fingerprints in the seventeenth century, but those observations weren't really connected to the idea that fingerprints themselves are unique to specific individuals and that no two people would share the same ones. J. C. A. Meyer, a German anatomist, published Anatomical Copper Plates with Appropriate Explanations. That's the actual title of the book, Anatomical Copper Plates with Appropriate Explanations, in sounds like it was a rip roaring picture book anyway. He described fingerprints as being unique, but also noted that they can appear similar to one another. So, in other words, on close examination you will see that they are unique, but on casual glance you may not be able to make that distinction easily. The nineteenth century saw a lot more work to define the qualities of fingerprints and how to classify them. How would you describe the fingerprints, how would you describe the grooves in such a way that it made sense? And then how would you classify fingerprints so that you could kind of categorize them, and how would you preserve impressions of them. All of these were ideas and practices that were developed in the eighteen hundreds. By the end of that century, Mark Twain was incorporating the idea of using fingerprints to identify a murderer and a couple of his books, And right at the cusp of the twentieth century, just before nineteen hundred, you had organizations starting to build out fingerprint files for the purposes of identifications. So the idea of using fingerprints to uh to ascertain the identity of someone you know they've left a fingerprint behind a scene, that had really started to take hold by the late nineteenth century, says the Sherlock Holmes era. The twentieth century saw a rapid development of technology in all different fields. Right, we see in the nineteen hundreds crazy amounts of innovation in all sorts of industries. But that included eventually things like digitizing records of fingerprint files, which would allow law enforcement to create the automated fingerprint identification system. And now in the United States, the Department of Homeland Security oversees a database containing more than one twenty million people's fingerprints. The FBI conducts more than three hundred thousand KORD searches per day against more than one forty million computerized fingerprint records. Uh some of those are criminals, some of those are civil, and so like civil fingerprints, you might have to submit for fingerprinting at when getting a a an i D like a state issued i D for example in the United States. The world's largest database of fingerprint information, not just fingerprint but biometric in general, actually belongs to a company called the Unique Identification Authority of India. It's really more of an organization, I guess I should say so that also includes face and biometric records and the goal to provide all one point to five billion residents of India with the option to record their biometric data for the purposes of providing reliable national i D documents. Participation in that database, by the way, is voluntary, so they aren't forced to submit to this uh In the citizens of India can opt into this system for the purposes of making it easier to get these kinds of national ideas. So that's the idea behind fingerprinting. This this concept of being able to look at the loops in the worlds and the various ridges and to compare them against a large database to see if there's a match. There were very familiar with that, and like I said, I did a full episode. So if you want to learn way more about the process of fingerprinting and identification through fingerprinting, go through the text of archives. There's an episode just about that. So let's move over to ballistics. Now, technically, ballistics is the science of projectiles and firearms. Within the context of forensics. We tend to use the term ballistics to talk about the various aspects of an investigation into a crime that included a gun being fired at least once, and a lot can go into that. One person I need to mention is a guy named Henry Goddard, and there actually were a couple of Henry Goddard's, So I'm not talking about the American psychologist who advocated for intelligence testing in the early twentieth century. I'm instead talking about a nineteenth century member of London's Bow Street Runners. And holy cow, this is a group that needs coverage in a show like Ridiculous History, not because it's ridiculous, but because it is fascinating. This is one of those things where I had heard about the Bow Street runners, but I hadn't really looked into it. And by the way, if someone comes in to tell me that no, it's Bow Street in London and Bow Street not Bow Street, I apologize. That's my American ignorance showing through. I'm gonna go with Bow Street because that's just how I assumed it was pronounced, but I fully admit it could be wrong. So quick history lesson. Leading up to the late seventeen hundreds, it was customary in London that if you happen to be a man, you were expected to participate in the policing of your own community. So if you saw a crime being commit did you were expected to intervene in that crime and apprehend the perpetrator and convict that person. You were also expected to send serve time in the night watch, which meant that between the hours of say eight or nine PM and dawn, you would have to patrol streets and make sure that that there were no suspicious people lurking about, or that if anyone was seen on the streets, that they had a valid reason to be out there and they weren't up to no good. And a lot of people were starting to get a little nervous about this because by the seventeen hundreds you had a new class that had formed in London. And previously you had the commoners and you had the nobility, and that was the way of things in the in England for quite some time. Uh and then by the Renaissance you were starting to see the rise of the middle class, and by the seventeen hundreds you the upper middle class. You had people who were wealthy. They weren't noble, but they owned a lot of wealth, whereas you had nobility that were they had noble titles, but some of them weren't very wealthy at all. So this really created confusion in England, where for the longest time social status was based upon nobility, and nobility tended to bring wealth along with it. Anyway, you had these upper class folks in London, men who were not terribly keen on the idea of having to patrol their city streets and getting involved in altercations that could involve violent criminals. You think, I didn't work so hard to become so successful to potentially get my skull caved in by a villain with a club. So I'm going to hire someone to go in my place, and people started to hire deputies. Well. Around the same time, royal proclamations had created a reward system for people who helped keep the peace by convicting criminals of various crimes, including various thefts, so this gave rise to an unofficial occupation called thief taker. Thief takers would often not just make money by pursuing convictions of criminals, but also essentially selling back stolen property to the rightful owners. So they would get money by putting the thief behind bars and get more money by selling the stolen property back to the person who owned in the first place. So then you had Henry and John Fielding and they had a house on Bow Street. Henry Fielding started to pay retainers to men who were either constables or ex constables to locate and arrest criminals, particularly violent criminals, and if you did that, you were entitled to the reward. So if you were one of the members of the Bow Street Runners and you apprehended someone, you convicted that person of a crime, you would get the reward there and the Fieldings hope that what they could do is managed this group and rain in any corruption to keep things on the level, and they essentially became a private police force of sorts, and over time they developed processes and procedures that would become the foundation of modern policing in many ways. Now, Goddard, who had mentioned before, was one of these bow street runners or policemen, and he identified a murderer in eighteen thirty five by linking a bullet recovered from a victim to the person who made the bullet, because in those days most people who owned guns made their own bullets. You did this by pouring molten lead into a two piece mold, to set it into that mold, and then you would, you know, forge a bullet. Goddard saw in the bullet, and imperfection that he reasoned was from the manufacturing process, which meant the mold itself would have evidence of that fault, and if you were to mold another bullet with that mold, you should be able to replicate the fault in it. So Goddard was able to get a confession from the suspect and one to convict action. It was only later that people pointed out his approach was not necessarily the most scientific, as similar molds could have produced a similar looking bullet. But it was an early example of ballistics and forensics. It's just it wasn't a terribly scientifically solid one. But you flash forward a century later and then you have Calvin Goddard, but no relation to Henry Goddard, whom I just talked about. Calvin Goddard was a scientist, a researcher, and a military officer, and in nineteen five he wrote an article titled Forensic Ballistics and described using a special type of microscope he had created called a comparison microscope when examining side by side specimens. Now, essentially a comparison microscope is too light. Microscopes connected by an optical bridge. So there are two uh ocular lenses, two eye pieces, so you look in one with each giant. It looks almost like binoculars, excepted some microscope. And it meant that you could put a sample under one and a sample under the second one, and pair of the two in a single view. And he used it to compare bullet casings or bullet shells and bullets recovered from crime scenes, and by being able to see both a bullet and it's casing, he could verify whether or not the bullet actually belonged to that casing by the markings. He could also if say you had recovered a firearm from a suspect and you were wondering if it was the same firearm as the one used in a crime, you could fire that into a soft target, retrieved the bullets, compare them side by side, so uh that would allow you to look at them in real time next to each other at a microscopic level. Previously, what you would have to do is look at one like the actual one that was found at the scene of a crime, and make note of any indentations or markings on the bullet, and then you would look at a second one separately. But that men, you had to rely upon your memory in part to make this comparison in and memories are faulty, so his technology would end up playing a vital role in several early twentieth century investigations, including the investigation into the infamous St. Valentine's Day massacre. Goddard was able to prove that the bullets that were fired in that crime did not come from police guns because the men who committed the murders were wearing Chicago police uniforms when they did it, but they said, well, no, these didn't come from the guns that belonged to police officers. Later on they were able to discover a gun that belonged to a mobster that did match the bullets that were fired during the St. Valentine's Day masacre. So it was one of the guns used in that terrible, terrible event. They were figured out it wasn't vigilante justice at all, it was a mob hit. Based upon the evidence, Godard would be asked to become the head of the first independent forensics science crime Lab, which was at Northwestern University in nineteen twenty nine. The lab later became known as the Scientific Crime Detection Laboratory of h AGO. Very influential lab. Now get a lot more to say about forensics science and its development over the years, but first let's take a quick break to thank our sponsor. One of the many things a ballistics expert in forensic studies would look at would be those marks left on a bullet after it has been fired from a gun. Modern guns have rifling in the barrels, which refers to grooves that are inside the barrel. They're meant to produce torque on a bullet, which forces the bullet to spin as it travels down the barrel, and it continues spinning when it emerges because a spinning projectile has a much more stable flight path due to behaving like a gyroscope. I talked about gyroscopes in recent episodes of tech Stuff. Essentially because of the conservation of angular momentum and objects spinning around an access of rotation resists changes in its orientation, so a spinning bullet will remain more true to its flight path. And a projectile fired from a smooth bore firearm which has no rifling on the inside of its gun barrel, but passing down this groove path essentially carves a pattern on a bullet. A bullets diameter is slightly larger than the board diameter of the barrel it is fired through. The bullet is of a softer material, so it will end up getting a pattern carved into it as it as as it's forced on this barrel at high velocity and begins to go into the spin. Investigators can actually count the number of grooves or impressions around the circumference of the bullet, and by looking down the length of a bullet from behind, the investigators can determine the twist direction of the rifling grooves inside the barrel, and this part of a gun barrel can wear down after use. That means that the patterns will end up being unique to specific guns. Even if you have two guns that are the same make and model, the wear pattern is going to be different for both of those so you will end up have different patterns actually imparted to the bullets fired out of those guns. So if investigators can retrieve bullets from a scene, they can potentially match those bullets to a specific firearm, assuming they also have possession of that firearm to compare the two, or they can use the patterns to potentially eliminate firearms that could not have produced those patterns. So, like I said before, the way you would typically do this is you have the suspect firearm, you fired it a few times, and you fire it into into a target that will preserve the integrity of the bullets. It's not designed to have the bullet break apart. So that way you have as good a sample as you possibly can. You compare the patterns on that bullet to the one that you have retrieved from the crime scene, and you look and see if they they are in fact similar enough to say they were both fired from the same weapon. Uh. Firearms also produced marks on cartridge cases, and no two firearms will do so exactly the same way. So cartridges will bear markings, they're different from rifling markings. They they might have something like a firing pin, Ambrussians, breach marks, extractor marks, and dejector marks. Depending upon the type of firearm you're talking about, surface characteristics created on the firearm itself from use will give it a uniqueness that other firearms won't reproduce. That's that where in Taro is telling you about um. But firearms also don't change super quickly, right. They do wear down over time, but it's not super super fast. Even if two are the same make and model, you're gonna have slight differences, like I said before, But they don't change so fast that you have to worry about identifying a gun. Well after a crime is committed, let's say that you have retrieved a bullet from the case of the crime scene, and let's say it's a cold case, like it's the case has gone cold and it's essentially shelved. And then later on you come across somebody and you're like I like this guy for that crime we never solved, you know, fifteen years ago, and this guy even had a gun that would have fired the bullets. It's the same style of gun that we suspect fired the bullets that we retrieved at that scene. Even though fifteen years have passed. You can fire that suspects gun and you can compare it against the bullet you retreat from the crime scene, and chances are there won't be so much wear and tear. Assuming it is the same gun, that you would be able to say, oh, it's the exact same firearm. So if you fire a gun once and you retreat the bullet, then you fire at ninety nine more times and you treat the one bullet, there should still be enough similarities between bullets one and one hundred for you to say they both definitely came from the same gun. In addition to studying bullets to determine if they were fired from a specific firearm, forensic investigators also examined bullet holes left it scenes to figure out where the person firing the gun was standing and how tall he or she was. Based on the evidence, the shape of a bullet hole gives us a lot of information. So some people might say, go, bullet holes are gonna be around, Well, that's not true unless the person firing the gun is firing at perfectly level at a ninety degree angle to whatever the surfaces that that ends up being hit by the bullet. Otherwise you're gonna get an elliptical shape from the bullet hole, and that elliptical shape will tell you a lot. It's it's angled, it will show that the bullet hit the wallet to bias. So you can determine the angle from which the bullet entered the wall, and if you have a suspect, you can use geometry to determine if that suspect could have been responsible. Not necessarily if they did or didn't do it, but you can at least say, well, is it possible that they did it. This is where you look at, say, bullet holes in the wall. You determine the angle from where the bullet entered the wall. You've figured out where what distance from the wall the shooter was, and you say, well, if the shooter was five ft ten, this makes sense. But if you start getting too short or too tall from that, then it wouldn't. The angle doesn't make any that's based upon what we know. So let's say that you've got a four ft three inch tall suspect. You might say, well, there's no way this person is too short for that to have worked out the way we believe it did. So that those bullet holes can tell you a lot of information, but you have to use geometry in order to do it, which means I would be really bad at it. I was terrible at geometry. It's great at trigonometry, but not so much at geometry. Anyway, these days, investigators may use advanced technologies like laser scanners to get really precise information from a crime scene in order to create a simulation to to view things like the angle of fire and the distance and that sort of stuff. I'll talk more about that in the next episode. However, other science and technology that relates to crimes in which a gun was fired might include detecting residue from gunshots. By the nineteen seventies, scientists started using scanning electron microscopes to do at I also talk about scanning electron microscopes in the next episode and talk about how those work. It's pretty fascinating stuff. But forensics goes beyond fingerprints and ballistics in the eighteen thirties, there was a chemist named James Marsh who developed a chemical test we called the Marsh test and it was specifically to detect the presence of arsenic and he developed the test after he determined the prevailing methodology was inferior after a pretty upsetting incident in his life and all had to do with a murder trial. In two there was a man who stood accused of having murdered his grandfather by poisoning his granddad's coffee with arsenic and James Marsh was called upon to do an investigation and present his findings to court, and he was meant to test the coffee for arsenic. Now, the standard at the time was that you would pass hydrogen sulfide through a sample fluid and that would create a reaction that would release hydrogen. The hydrogen would carry particles of arsenic as it bubbled up through the sample. And it's in gas form, so it passes through you know it'll it would just dissipate if you didn't have anything else attached to it. But you would have your your device set up so that the gas is passing through a line like a glass tube for example, and you would heat the tube, and you would also burn off the hydrogen as it came out the other end of the two and traces of arsenic would remain as a precipitate that would be collected and you could use it what they would call an arsenic mirror and create the sort of blackish uh finish on a surface. But the problem was it wouldn't keep indefinitely. So Marsh conducts this test. He detects arsenic in the coffee, but by the time he was called to present to the jury, the evidence he had collected had deteriorated, and it deterior to the point where the jury didn't see the evidence, so they suspect was ultimately released of charges, and Marsh figured there had to be a better way, so he developed what we now call the Marsh test, and he stuck with a chemical reaction approach. He experimented, and he found that if he combined a sample that had arsenic in it and he put that in with some zinc that had no arsenic in it at all, arsenic free zinc, and then added sulfuric acid, it would create arsene gas, and burning off that gas would produce pure metallic arsenic and if that were to come in contact with a cold surface, it would leave behind a silvery black coating. And it was a sensitive enough test that could detect quantities of arsenic as small as one of a milligram, which is pretty nifty. Now, if there were no arsenic in the sample, you wouldn't produce this gas, so you wouldn't have that silvery residue. So chemical analysis is another important part of ensics science, and arsenic is just one of dozens of different chemicals investigators might have to search for at a crime scene. Another important element in forensics has to do with blood. Clearly, that becomes a very important element in investigations. During the nineteenth century, Dr Ludwig Carl Tichman developed a test to determine if a stain actually was dried blood or maybe it's mud or something else. And this is a test we call the Tychman test. Tend to name things after the people who proposed them. So Dr Tychman researched how organic compounds contained in human blood could crystallize. One of those compounds is called human and so Tychman developed a test in which he used a strong acetic acid, which is present in stuff like vinegar, for example, and you combine that with dried blood, and that would form human crystals. The reaction between the to acid and the blood would make these Heman crystals form. So if you're investigating a crime and you see some stains that could be dried blood, but you're not sure, you could use the Tykeman test and confirm that suspicion. It doesn't tell you what type of blood it is, it doesn't let you classify it in any way, but it would let you at least verify that in fact, the stain you're looking at is composed at least in part by blood. So if no Heman crystals formed as a result, you could disregard the stain and just say, well, I don't know what it is, but it sure ain't blood. In nineteen o one, and Austrian scientists named Carl Lnsteiner was studying blood and why sometimes when blood from one individual would be given to another individual, the blood would clump together in a process called a glutination. The clumping could create toxic reactions, which made transfusions really dangerous, and physicians have been practicing transfusions for quite some time, but no one was really sure up to that point why some transfusions seem to work and other transfusions would lead to pretty nasty outcomes, sometimes death. Landstein Are discovered that the clumping was an immunological reaction, and it was when the receiver of a blood transfusion has antibodies against components inside the donor blood, and that led to the discovery of different protein molecules within different types of blood and ultimately lead to classifying blood into groups such as A, B, A B, and OH. So, if you have type A blood, you have A antigens and BE antibodies, meaning you can accept A blood, but you cannot accept BE blood because you would react very poorly to that. Um BE blood is the opposite. You have BE antigens and A antibodies, and then A B. You have both A and B engines and antibodies. You're You're the universal received You can receive blood from any donor, and then type OH you lack the antigens and antibodies. You're the universal donor. Or. You really you don't have the antigen so you don't have to worry about uh. Like, if you're an donor, you can donate blood to anyone. Anyone can accept oh blood, though you can only accept OH blood in return fun times. Lensteiner would win a Nobel Prize in nineteen thirty for his work, and forensic scientists had a new way to examine blood to help them narrow down suspects or differentiate between a victim's blood and the blood of a suspect. Up to that point, you couldn't be sure. You might come up on a crime scene and it might be blood on the crime scene, but you don't know how much of that belonged to the victim, and and if what if any of it belonged to someone else. This allowed for testing of different proteins, which would tell you, oh, this is a type A versus type B, and would tell you if more than one person's blood were present at a crime scene. So very a useful, especially later on when you are looking up potentially identifying someone, although keep in mind the percentages of people with specific types of blood are such that you can't narrow it down to a specific individual. Just because a person might have the same blood type as blood found at the scene of a crime doesn't necessarily mean that the blood came from that person, because lots of people have those blood types it would take more specific evidence to be able to narrow that down. I'll talk more about that in a second, but first let's take another quick break to thank our sponsor. In h o Albrecht was experimenting with a chemical called luminol, a luminescent chemical, and he was experimenting with it in a solution of hydrogen peroxide, and he discovered that blood would increase the luminescence of luminol, which means it would it would cause the luminol to glow brighter. Later, other scientists determined that hematin, a pigment in blood that contains iron in it, was reacting with this luminol chemically and that chemical reaction was creating this brighter luminescence, and that became useful in forensic investigations when investigators were looking for trace amounts of blood at a scene it may not be easily visible, or maybe that someone tried to clean it up, because luminol can actually detect those trace evidence leavings of blood even if someone tried to clean stuff up. It does require making the crime scene as dark as possible so you can detect the luminescence and the glow lasts for less than a minute. But if you do a quick spritzing of luminol and hydrogen peroxide as a solution against the same spot, it will glow again. It doesn't exhaust the supply of iron necessarily on one spritzing, so uh, if you see a glow, you can reapply LIE. By the nineteen eighties, scientists were starting to develop practical tests that could analyze DNA for the purposes of forensic tests. And DNA is d ox a ribonucleic acid, which is the carrier of genetic information. I'm pretty sure you all are familiar with that, but it always is good to just kind of jump on that again. DNA contains the fundamental genetic identifiers that can be of crucial importance in an investigation. Now, most of your DNA matches my DNA, or the person in closest proximity to you, or the person most far away from you possible. We share an enormous amount of common DNA. The differences between individuals between humans are carried by about three million bases in our DNA. That that's equivalent to about one tenth of one per cent of all our DNA. So the vast majority of our DNA is identical to each other. It's only that one tenth of one percent that makes you you, which is kind of cool and and interesting. Those differences can help eliminate a suspect from an investigation, or it can help support a case for investigating the matter further if there's a match. DNA comes from organic material like blood or body fluids, from skin, from hair, stuff like that. The development of polymerase chain reaction or PCR techniques helped with DNA investigations a lot. PCR is a method for copying specific DNA regions in vitro that means in a test too, as opposed to in an organism. PCR is used for lots of different stuff, not just forensic investigations because it allows you to copy and duplicate DNA, but in forensics it can be used to make copies of sample DNA for analysis to compare DNA gathered at a crime scene with DNA from like a suspect. Some crime scenes may only have small samples of DNA that you can work with, so it's important to be able to duplicate that DNA in order for you to have enough of a sample size to run your various analyzes. In nineteen nine, DNA evidence was used to exonerate a man named Gary Dotson who had been convicted of rape in the late nineteen seventies. Kathleen Crowell, who was the presumed victim of this crime, ended up later saying she had actually made up a story about being raped. What had happened was that she and her boyfriend had engaged in consensual sex, but she was worried that she might end up pregnant, and she was terrified of what that would mean. She was a teenager at the time. She was scared about how her parents and community would react, and preemptively she made the claim that she had been assaulted by a group of three men and raped by one of them, and she just made it up entirely. Uh. She was brought in to the police station to talk to police officers who wanted to get a sketch artist there to get a sketch of her, her presumed attacker, and so she started making up a description. The description she made up happened to kind of resemble someone who was in a collection of mug shots at that police station, and it was a guy named Gary Dotson who had run a follow the law previously, but she had made this whole story up. It's just so happened that the person that she was describing happened to look like this guy now. According to Crowell, the police pressured her into identifying Dotson as her rapist, and she was still scared of telling the truth to anyone, so she went along with it. Dotson would end up being tried and convicted of rape and sent to prison, and Krowell would later recant her accusation. In five she said she was overcome with guilt about what she had done to him and that she had decided that it was enough was enough, she had to come forward and tell the truth. And prosecutors weren't too eager to do that. They I guess partly were worried that it was going to reflect really poorly on them. The trial had included testimony from various forensics experts, and it would mean that they were either fabricating evidence or very much misidentifying things, and that it was going to look terrible to them. So anyway, a judge ended up releasing Dotson on a one hundred thousand dollar bond, but Dotson wasn't truly exonerated until DNA tests in nineteen nine proved that he wasn't involved. So, in other words, his accuser had come back up and said, I made it all up. He didn't do anything to me. I was scared, and I came up with this story that I thought was going to help things. I did not intend for this to happen. And some of the legal community dismissed her statement. They said, oh, she's unstable, she's you can't rely upon her statements. And it wasn't until the DNA evidence came out that said Dodson could not have been the person that was accused of this crime because his DNA did not match the DNA that was gathered in the wake of her accusation. The whole story, by the way, goes into way more crazy detail and and there are a lot more twists and turns and a lot of tragedy involved in it as well. It's sad, it's an infuriating story. There's an excellent treatment of the story over at Northwestern University's Prints Care School of Law website. It has the title first DNA Exoneration. So if you want to read all about it, and it is an exhaustive account, uh, you should check that out, because it is fascinating as well as upsetting. The emergence of DNA led to the development of quality control guidelines for DNA labs and forensic investigators. It became clear that in order to make effective use of this information, of this knowledge of DNA, they had to make sure they created very straightforward, very uh standardized approaches to to reduce the possibility of destroying or altering evidence, either by accident or on purpose. You know, do something where you can document it step by step by steps so people can make certain that you did everything correctly, so that your conclusions can be seen as valid. Now, while these sciences, sciences and processes were developing, police forces and other law enforcement agencies were actually working to formalize the development and deployment of investigations. How do you teach investigators these these processes, Because a lot of them were developed independently, they are being made use in specific police forces, but they weren't necessarily shared. How did that come about? Well, in the nineteenth century, if you were in the eighteen hundreds and you were a forensic researcher, you were connected to some sort of law enforcement group, whether private or public. You were a auntly self taught. You got hold of whatever information you could find and you would study it or you would develop your own ideas in your own processes. It was very informal. One of the earliest formal schools in forensics was created by a guy named Rudolph Archibald Rice. He was a professor at the University of a Lausan, Switzerland. He had studied chemistry. At that university, he earned a doctorate in the field, and he began turning his scientific mind towards criminal investigation. He studied the discoveries of other criminologists, and in nineteen o nine he founded the Institute of Scientific Police. Other universities in Europe began to found their own forensic studies curricula, but then you had World War One and World War Two, and that wiped out a lot of those efforts. The Institute of Scientific Police survived the two World Wars because Switzerland was neutral in both of those. Today this school has a different name. It's called the School of Criminal Sciences. The same organization, new name, I mean, obviously updated with the more modern approaches. Rice in his time would actually publish a book about investigative techniques used in the event of burglaries and homicides, and he had planned future volumes to cover other types of crimes like counterfeiting, as well as other police matters like organizing a police force, but he ended up putting all of that on hold. The Serbian government requested his assistance to investigate war crimes committed by the armies of Austria Hungary during the Serbian War, and so he never finished those books. In An American named August Volmer, who was chief of police in Los Angeles, California, founded the first American police crime laboratory, which actually predated the FBI's crime lab by eight years. The FBI was formed in nineteen o eight, but it would not have its own crime lab till nineteen thirty two. It was the early nineteen thirties when colleges and universities began offering degrees in police sciences and minalistics, and in nineteen fifty the University of California at Berkeley created an early department of Criminology over in Chicago. Around that same time, academics founded the American Academy of Forensic Science, and today there are numerous colleges that offer coursework and forensic science. There are labs dedicated to the purpose of applying the scientific method when it comes to the investigation of crime, and there are companies that produce technology with the primary purpose of aiding in criminal investigations. And in our next episode, I will take a closer look at some of those actual technologies, some really cool ones, though they may not be exactly the same as what we see in television and film. That's it for this episode. If you guys have suggestions for future episodes of tech Stuff, maybe it's a technology, maybe it's a person or a company you want me to cover, send me a message emails great. The email address you can use as tech stuff at how stuff works dot com. You can drop me a line on Twitter or Facebook handle for both of those is tech Stuff hs W. Don't forget we have a merchandise store. It's at T public dot com. That's T E E public dot com. Maybe you've always wanted a tech stuff tote bag or a phone case or a coffee mug, Well you can get those and more at t public dot com slash tech stuff. We have a lot of different designs up there. Every purchase you make goes to help the show, and you get something cool and return so we really appreciate it, and don't forget Follow us on Instagram please, and I'll talk to you again really soon. For more on this and thousands of other topics. Is that how stuff works dot com

Get in touch with technology with tech Stuff from how stuff Works dot com. Hey there, and welcome to tech Stuff. I am your host, Jonathan Strickland. I'm an executive producer with how Stuff Works in I love all things tech, though today we're gonna be talking about a branch of technology that gets up. I'm pretty grim and pretty serious. Uh, this is a listener request. Listener Hakim asked that I do an episode about forensic technology, so I'm actually gonna do a pair of episodes. It is fascinating stuff and it's definitely not quite the same as what we see in depictions on film or in television shows. That's not a big surprise. We've covered multiple times how technology in pop culture is very different from what we see in reality. But in this episode, I'm going to specifically focus on the history of forensics, and in the next episode we'll talk about some of the cutting edge technologies that are used in for psick investigations today. So forensics, first of all, has a few different definitions. If you are being very literal, it can mean debate or discussion in Latin, but as we tend to use it today, we refer to it as the science with regard to detecting and solving crimes. So not just if a crime has occurred, but how did a crime occur, how did it unfold in time, who was involved? That sort of stuff. And like all sciences, forensics can trace its history back far before the formal codification of the scientific method, and this involves lots of different ideas and processes for different elements of investigation developing at various times throughout history. Like most things, forensics involved a lot of different ideas being tested throughout centuries before maturing as a collection of practices. So one of the easy ideas we can talk about, because there are a lot of different independent threads that converge to become forensics. On easy entry point is a discussion about fingerprints and developing the skills and technology to detect and identify them and classify them in the context of criminal investigations. Now, I've done a full episode on fingerprinting in the past, so I'll give more of a short overview of the whole thing here. There are records that actually indicate that handprints were used as evidence and investigations for burglary back in China more than two thousand years ago, and the book with the English title Universal History, which was published in Persia in the th hundreds, mentioned the practice of identifying people based upon their fingerprints. European anatomists and philosophers made observations about fingerprints in the seventeenth century, but those observations weren't really connected to the idea that fingerprints themselves are unique to specific individuals and that no two people would share the same ones. J. C. A. Meyer, a German anatomist, published Anatomical Copper Plates with Appropriate Explanations. That's the actual title of the book, Anatomical Copper Plates with Appropriate Explanations, in sounds like it was a rip roaring picture book anyway. He described fingerprints as being unique, but also noted that they can appear similar to one another. So, in other words, on close examination you will see that they are unique, but on casual glance you may not be able to make that distinction easily. The nineteenth century saw a lot more work to define the qualities of fingerprints and how to classify them. How would you describe the fingerprints, how would you describe the grooves in such a way that it made sense? And then how would you classify fingerprints so that you could kind of categorize them, and how would you preserve impressions of them. All of these were ideas and practices that were developed in the eighteen hundreds. By the end of that century, Mark Twain was incorporating the idea of using fingerprints to identify a murderer and a couple of his books, And right at the cusp of the twentieth century, just before nineteen hundred, you had organizations starting to build out fingerprint files for the purposes of identifications. So the idea of using fingerprints to uh to ascertain the identity of someone you know they've left a fingerprint behind a scene, that had really started to take hold by the late nineteenth century, says the Sherlock Holmes era. The twentieth century saw a rapid development of technology in all different fields. Right, we see in the nineteen hundreds crazy amounts of innovation in all sorts of industries. But that included eventually things like digitizing records of fingerprint files, which would allow law enforcement to create the automated fingerprint identification system. And now in the United States, the Department of Homeland Security oversees a database containing more than one twenty million people's fingerprints. The FBI conducts more than three hundred thousand KORD searches per day against more than one forty million computerized fingerprint records. Uh some of those are criminals, some of those are civil, and so like civil fingerprints, you might have to submit for fingerprinting at when getting a a an i D like a state issued i D for example in the United States. The world's largest database of fingerprint information, not just fingerprint but biometric in general, actually belongs to a company called the Unique Identification Authority of India. It's really more of an organization, I guess I should say so that also includes face and biometric records and the goal to provide all one point to five billion residents of India with the option to record their biometric data for the purposes of providing reliable national i D documents. Participation in that database, by the way, is voluntary, so they aren't forced to submit to this uh In the citizens of India can opt into this system for the purposes of making it easier to get these kinds of national ideas. So that's the idea behind fingerprinting. This this concept of being able to look at the loops in the worlds and the various ridges and to compare them against a large database to see if there's a match. There were very familiar with that, and like I said, I did a full episode. So if you want to learn way more about the process of fingerprinting and identification through fingerprinting, go through the text of archives. There's an episode just about that. So let's move over to ballistics. Now, technically, ballistics is the science of projectiles and firearms. Within the context of forensics. We tend to use the term ballistics to talk about the various aspects of an investigation into a crime that included a gun being fired at least once, and a lot can go into that. One person I need to mention is a guy named Henry Goddard, and there actually were a couple of Henry Goddard's, So I'm not talking about the American psychologist who advocated for intelligence testing in the early twentieth century. I'm instead talking about a nineteenth century member of London's Bow Street Runners. And holy cow, this is a group that needs coverage in a show like Ridiculous History, not because it's ridiculous, but because it is fascinating. This is one of those things where I had heard about the Bow Street runners, but I hadn't really looked into it. And by the way, if someone comes in to tell me that no, it's Bow Street in London and Bow Street not Bow Street, I apologize. That's my American ignorance showing through. I'm gonna go with Bow Street because that's just how I assumed it was pronounced, but I fully admit it could be wrong. So quick history lesson. Leading up to the late seventeen hundreds, it was customary in London that if you happen to be a man, you were expected to participate in the policing of your own community. So if you saw a crime being commit did you were expected to intervene in that crime and apprehend the perpetrator and convict that person. You were also expected to send serve time in the night watch, which meant that between the hours of say eight or nine PM and dawn, you would have to patrol streets and make sure that that there were no suspicious people lurking about, or that if anyone was seen on the streets, that they had a valid reason to be out there and they weren't up to no good. And a lot of people were starting to get a little nervous about this because by the seventeen hundreds you had a new class that had formed in London. And previously you had the commoners and you had the nobility, and that was the way of things in the in England for quite some time. Uh and then by the Renaissance you were starting to see the rise of the middle class, and by the seventeen hundreds you the upper middle class. You had people who were wealthy. They weren't noble, but they owned a lot of wealth, whereas you had nobility that were they had noble titles, but some of them weren't very wealthy at all. So this really created confusion in England, where for the longest time social status was based upon nobility, and nobility tended to bring wealth along with it. Anyway, you had these upper class folks in London, men who were not terribly keen on the idea of having to patrol their city streets and getting involved in altercations that could involve violent criminals. You think, I didn't work so hard to become so successful to potentially get my skull caved in by a villain with a club. So I'm going to hire someone to go in my place, and people started to hire deputies. Well. Around the same time, royal proclamations had created a reward system for people who helped keep the peace by convicting criminals of various crimes, including various thefts, so this gave rise to an unofficial occupation called thief taker. Thief takers would often not just make money by pursuing convictions of criminals, but also essentially selling back stolen property to the rightful owners. So they would get money by putting the thief behind bars and get more money by selling the stolen property back to the person who owned in the first place. So then you had Henry and John Fielding and they had a house on Bow Street. Henry Fielding started to pay retainers to men who were either constables or ex constables to locate and arrest criminals, particularly violent criminals, and if you did that, you were entitled to the reward. So if you were one of the members of the Bow Street Runners and you apprehended someone, you convicted that person of a crime, you would get the reward there and the Fieldings hope that what they could do is managed this group and rain in any corruption to keep things on the level, and they essentially became a private police force of sorts, and over time they developed processes and procedures that would become the foundation of modern policing in many ways. Now, Goddard, who had mentioned before, was one of these bow street runners or policemen, and he identified a murderer in eighteen thirty five by linking a bullet recovered from a victim to the person who made the bullet, because in those days most people who owned guns made their own bullets. You did this by pouring molten lead into a two piece mold, to set it into that mold, and then you would, you know, forge a bullet. Goddard saw in the bullet, and imperfection that he reasoned was from the manufacturing process, which meant the mold itself would have evidence of that fault, and if you were to mold another bullet with that mold, you should be able to replicate the fault in it. So Goddard was able to get a confession from the suspect and one to convict action. It was only later that people pointed out his approach was not necessarily the most scientific, as similar molds could have produced a similar looking bullet. But it was an early example of ballistics and forensics. It's just it wasn't a terribly scientifically solid one. But you flash forward a century later and then you have Calvin Goddard, but no relation to Henry Goddard, whom I just talked about. Calvin Goddard was a scientist, a researcher, and a military officer, and in nineteen five he wrote an article titled Forensic Ballistics and described using a special type of microscope he had created called a comparison microscope when examining side by side specimens. Now, essentially a comparison microscope is too light. Microscopes connected by an optical bridge. So there are two uh ocular lenses, two eye pieces, so you look in one with each giant. It looks almost like binoculars, excepted some microscope. And it meant that you could put a sample under one and a sample under the second one, and pair of the two in a single view. And he used it to compare bullet casings or bullet shells and bullets recovered from crime scenes, and by being able to see both a bullet and it's casing, he could verify whether or not the bullet actually belonged to that casing by the markings. He could also if say you had recovered a firearm from a suspect and you were wondering if it was the same firearm as the one used in a crime, you could fire that into a soft target, retrieved the bullets, compare them side by side, so uh that would allow you to look at them in real time next to each other at a microscopic level. Previously, what you would have to do is look at one like the actual one that was found at the scene of a crime, and make note of any indentations or markings on the bullet, and then you would look at a second one separately. But that men, you had to rely upon your memory in part to make this comparison in and memories are faulty, so his technology would end up playing a vital role in several early twentieth century investigations, including the investigation into the infamous St. Valentine's Day massacre. Goddard was able to prove that the bullets that were fired in that crime did not come from police guns because the men who committed the murders were wearing Chicago police uniforms when they did it, but they said, well, no, these didn't come from the guns that belonged to police officers. Later on they were able to discover a gun that belonged to a mobster that did match the bullets that were fired during the St. Valentine's Day masacre. So it was one of the guns used in that terrible, terrible event. They were figured out it wasn't vigilante justice at all, it was a mob hit. Based upon the evidence, Godard would be asked to become the head of the first independent forensics science crime Lab, which was at Northwestern University in nineteen twenty nine. The lab later became known as the Scientific Crime Detection Laboratory of h AGO. Very influential lab. Now get a lot more to say about forensics science and its development over the years, but first let's take a quick break to thank our sponsor. One of the many things a ballistics expert in forensic studies would look at would be those marks left on a bullet after it has been fired from a gun. Modern guns have rifling in the barrels, which refers to grooves that are inside the barrel. They're meant to produce torque on a bullet, which forces the bullet to spin as it travels down the barrel, and it continues spinning when it emerges because a spinning projectile has a much more stable flight path due to behaving like a gyroscope. I talked about gyroscopes in recent episodes of tech Stuff. Essentially because of the conservation of angular momentum and objects spinning around an access of rotation resists changes in its orientation, so a spinning bullet will remain more true to its flight path. And a projectile fired from a smooth bore firearm which has no rifling on the inside of its gun barrel, but passing down this groove path essentially carves a pattern on a bullet. A bullets diameter is slightly larger than the board diameter of the barrel it is fired through. The bullet is of a softer material, so it will end up getting a pattern carved into it as it as as it's forced on this barrel at high velocity and begins to go into the spin. Investigators can actually count the number of grooves or impressions around the circumference of the bullet, and by looking down the length of a bullet from behind, the investigators can determine the twist direction of the rifling grooves inside the barrel, and this part of a gun barrel can wear down after use. That means that the patterns will end up being unique to specific guns. Even if you have two guns that are the same make and model, the wear pattern is going to be different for both of those so you will end up have different patterns actually imparted to the bullets fired out of those guns. So if investigators can retrieve bullets from a scene, they can potentially match those bullets to a specific firearm, assuming they also have possession of that firearm to compare the two, or they can use the patterns to potentially eliminate firearms that could not have produced those patterns. So, like I said before, the way you would typically do this is you have the suspect firearm, you fired it a few times, and you fire it into into a target that will preserve the integrity of the bullets. It's not designed to have the bullet break apart. So that way you have as good a sample as you possibly can. You compare the patterns on that bullet to the one that you have retrieved from the crime scene, and you look and see if they they are in fact similar enough to say they were both fired from the same weapon. Uh. Firearms also produced marks on cartridge cases, and no two firearms will do so exactly the same way. So cartridges will bear markings, they're different from rifling markings. They they might have something like a firing pin, Ambrussians, breach marks, extractor marks, and dejector marks. Depending upon the type of firearm you're talking about, surface characteristics created on the firearm itself from use will give it a uniqueness that other firearms won't reproduce. That's that where in Taro is telling you about um. But firearms also don't change super quickly, right. They do wear down over time, but it's not super super fast. Even if two are the same make and model, you're gonna have slight differences, like I said before, But they don't change so fast that you have to worry about identifying a gun. Well after a crime is committed, let's say that you have retrieved a bullet from the case of the crime scene, and let's say it's a cold case, like it's the case has gone cold and it's essentially shelved. And then later on you come across somebody and you're like I like this guy for that crime we never solved, you know, fifteen years ago, and this guy even had a gun that would have fired the bullets. It's the same style of gun that we suspect fired the bullets that we retrieved at that scene. Even though fifteen years have passed. You can fire that suspects gun and you can compare it against the bullet you retreat from the crime scene, and chances are there won't be so much wear and tear. Assuming it is the same gun, that you would be able to say, oh, it's the exact same firearm. So if you fire a gun once and you retreat the bullet, then you fire at ninety nine more times and you treat the one bullet, there should still be enough similarities between bullets one and one hundred for you to say they both definitely came from the same gun. In addition to studying bullets to determine if they were fired from a specific firearm, forensic investigators also examined bullet holes left it scenes to figure out where the person firing the gun was standing and how tall he or she was. Based on the evidence, the shape of a bullet hole gives us a lot of information. So some people might say, go, bullet holes are gonna be around, Well, that's not true unless the person firing the gun is firing at perfectly level at a ninety degree angle to whatever the surfaces that that ends up being hit by the bullet. Otherwise you're gonna get an elliptical shape from the bullet hole, and that elliptical shape will tell you a lot. It's it's angled, it will show that the bullet hit the wallet to bias. So you can determine the angle from which the bullet entered the wall, and if you have a suspect, you can use geometry to determine if that suspect could have been responsible. Not necessarily if they did or didn't do it, but you can at least say, well, is it possible that they did it. This is where you look at, say, bullet holes in the wall. You determine the angle from where the bullet entered the wall. You've figured out where what distance from the wall the shooter was, and you say, well, if the shooter was five ft ten, this makes sense. But if you start getting too short or too tall from that, then it wouldn't. The angle doesn't make any that's based upon what we know. So let's say that you've got a four ft three inch tall suspect. You might say, well, there's no way this person is too short for that to have worked out the way we believe it did. So that those bullet holes can tell you a lot of information, but you have to use geometry in order to do it, which means I would be really bad at it. I was terrible at geometry. It's great at trigonometry, but not so much at geometry. Anyway, these days, investigators may use advanced technologies like laser scanners to get really precise information from a crime scene in order to create a simulation to to view things like the angle of fire and the distance and that sort of stuff. I'll talk more about that in the next episode. However, other science and technology that relates to crimes in which a gun was fired might include detecting residue from gunshots. By the nineteen seventies, scientists started using scanning electron microscopes to do at I also talk about scanning electron microscopes in the next episode and talk about how those work. It's pretty fascinating stuff. But forensics goes beyond fingerprints and ballistics in the eighteen thirties, there was a chemist named James Marsh who developed a chemical test we called the Marsh test and it was specifically to detect the presence of arsenic and he developed the test after he determined the prevailing methodology was inferior after a pretty upsetting incident in his life and all had to do with a murder trial. In two there was a man who stood accused of having murdered his grandfather by poisoning his granddad's coffee with arsenic and James Marsh was called upon to do an investigation and present his findings to court, and he was meant to test the coffee for arsenic. Now, the standard at the time was that you would pass hydrogen sulfide through a sample fluid and that would create a reaction that would release hydrogen. The hydrogen would carry particles of arsenic as it bubbled up through the sample. And it's in gas form, so it passes through you know it'll it would just dissipate if you didn't have anything else attached to it. But you would have your your device set up so that the gas is passing through a line like a glass tube for example, and you would heat the tube, and you would also burn off the hydrogen as it came out the other end of the two and traces of arsenic would remain as a precipitate that would be collected and you could use it what they would call an arsenic mirror and create the sort of blackish uh finish on a surface. But the problem was it wouldn't keep indefinitely. So Marsh conducts this test. He detects arsenic in the coffee, but by the time he was called to present to the jury, the evidence he had collected had deteriorated, and it deterior to the point where the jury didn't see the evidence, so they suspect was ultimately released of charges, and Marsh figured there had to be a better way, so he developed what we now call the Marsh test, and he stuck with a chemical reaction approach. He experimented, and he found that if he combined a sample that had arsenic in it and he put that in with some zinc that had no arsenic in it at all, arsenic free zinc, and then added sulfuric acid, it would create arsene gas, and burning off that gas would produce pure metallic arsenic and if that were to come in contact with a cold surface, it would leave behind a silvery black coating. And it was a sensitive enough test that could detect quantities of arsenic as small as one of a milligram, which is pretty nifty. Now, if there were no arsenic in the sample, you wouldn't produce this gas, so you wouldn't have that silvery residue. So chemical analysis is another important part of ensics science, and arsenic is just one of dozens of different chemicals investigators might have to search for at a crime scene. Another important element in forensics has to do with blood. Clearly, that becomes a very important element in investigations. During the nineteenth century, Dr Ludwig Carl Tichman developed a test to determine if a stain actually was dried blood or maybe it's mud or something else. And this is a test we call the Tychman test. Tend to name things after the people who proposed them. So Dr Tychman researched how organic compounds contained in human blood could crystallize. One of those compounds is called human and so Tychman developed a test in which he used a strong acetic acid, which is present in stuff like vinegar, for example, and you combine that with dried blood, and that would form human crystals. The reaction between the to acid and the blood would make these Heman crystals form. So if you're investigating a crime and you see some stains that could be dried blood, but you're not sure, you could use the Tykeman test and confirm that suspicion. It doesn't tell you what type of blood it is, it doesn't let you classify it in any way, but it would let you at least verify that in fact, the stain you're looking at is composed at least in part by blood. So if no Heman crystals formed as a result, you could disregard the stain and just say, well, I don't know what it is, but it sure ain't blood. In nineteen o one, and Austrian scientists named Carl Lnsteiner was studying blood and why sometimes when blood from one individual would be given to another individual, the blood would clump together in a process called a glutination. The clumping could create toxic reactions, which made transfusions really dangerous, and physicians have been practicing transfusions for quite some time, but no one was really sure up to that point why some transfusions seem to work and other transfusions would lead to pretty nasty outcomes, sometimes death. Landstein Are discovered that the clumping was an immunological reaction, and it was when the receiver of a blood transfusion has antibodies against components inside the donor blood, and that led to the discovery of different protein molecules within different types of blood and ultimately lead to classifying blood into groups such as A, B, A B, and OH. So, if you have type A blood, you have A antigens and BE antibodies, meaning you can accept A blood, but you cannot accept BE blood because you would react very poorly to that. Um BE blood is the opposite. You have BE antigens and A antibodies, and then A B. You have both A and B engines and antibodies. You're You're the universal received You can receive blood from any donor, and then type OH you lack the antigens and antibodies. You're the universal donor. Or. You really you don't have the antigen so you don't have to worry about uh. Like, if you're an donor, you can donate blood to anyone. Anyone can accept oh blood, though you can only accept OH blood in return fun times. Lensteiner would win a Nobel Prize in nineteen thirty for his work, and forensic scientists had a new way to examine blood to help them narrow down suspects or differentiate between a victim's blood and the blood of a suspect. Up to that point, you couldn't be sure. You might come up on a crime scene and it might be blood on the crime scene, but you don't know how much of that belonged to the victim, and and if what if any of it belonged to someone else. This allowed for testing of different proteins, which would tell you, oh, this is a type A versus type B, and would tell you if more than one person's blood were present at a crime scene. So very a useful, especially later on when you are looking up potentially identifying someone, although keep in mind the percentages of people with specific types of blood are such that you can't narrow it down to a specific individual. Just because a person might have the same blood type as blood found at the scene of a crime doesn't necessarily mean that the blood came from that person, because lots of people have those blood types it would take more specific evidence to be able to narrow that down. I'll talk more about that in a second, but first let's take another quick break to thank our sponsor. In h o Albrecht was experimenting with a chemical called luminol, a luminescent chemical, and he was experimenting with it in a solution of hydrogen peroxide, and he discovered that blood would increase the luminescence of luminol, which means it would it would cause the luminol to glow brighter. Later, other scientists determined that hematin, a pigment in blood that contains iron in it, was reacting with this luminol chemically and that chemical reaction was creating this brighter luminescence, and that became useful in forensic investigations when investigators were looking for trace amounts of blood at a scene it may not be easily visible, or maybe that someone tried to clean it up, because luminol can actually detect those trace evidence leavings of blood even if someone tried to clean stuff up. It does require making the crime scene as dark as possible so you can detect the luminescence and the glow lasts for less than a minute. But if you do a quick spritzing of luminol and hydrogen peroxide as a solution against the same spot, it will glow again. It doesn't exhaust the supply of iron necessarily on one spritzing, so uh, if you see a glow, you can reapply LIE. By the nineteen eighties, scientists were starting to develop practical tests that could analyze DNA for the purposes of forensic tests. And DNA is d ox a ribonucleic acid, which is the carrier of genetic information. I'm pretty sure you all are familiar with that, but it always is good to just kind of jump on that again. DNA contains the fundamental genetic identifiers that can be of crucial importance in an investigation. Now, most of your DNA matches my DNA, or the person in closest proximity to you, or the person most far away from you possible. We share an enormous amount of common DNA. The differences between individuals between humans are carried by about three million bases in our DNA. That that's equivalent to about one tenth of one per cent of all our DNA. So the vast majority of our DNA is identical to each other. It's only that one tenth of one percent that makes you you, which is kind of cool and and interesting. Those differences can help eliminate a suspect from an investigation, or it can help support a case for investigating the matter further if there's a match. DNA comes from organic material like blood or body fluids, from skin, from hair, stuff like that. The development of polymerase chain reaction or PCR techniques helped with DNA investigations a lot. PCR is a method for copying specific DNA regions in vitro that means in a test too, as opposed to in an organism. PCR is used for lots of different stuff, not just forensic investigations because it allows you to copy and duplicate DNA, but in forensics it can be used to make copies of sample DNA for analysis to compare DNA gathered at a crime scene with DNA from like a suspect. Some crime scenes may only have small samples of DNA that you can work with, so it's important to be able to duplicate that DNA in order for you to have enough of a sample size to run your various analyzes. In nineteen nine, DNA evidence was used to exonerate a man named Gary Dotson who had been convicted of rape in the late nineteen seventies. Kathleen Crowell, who was the presumed victim of this crime, ended up later saying she had actually made up a story about being raped. What had happened was that she and her boyfriend had engaged in consensual sex, but she was worried that she might end up pregnant, and she was terrified of what that would mean. She was a teenager at the time. She was scared about how her parents and community would react, and preemptively she made the claim that she had been assaulted by a group of three men and raped by one of them, and she just made it up entirely. Uh. She was brought in to the police station to talk to police officers who wanted to get a sketch artist there to get a sketch of her, her presumed attacker, and so she started making up a description. The description she made up happened to kind of resemble someone who was in a collection of mug shots at that police station, and it was a guy named Gary Dotson who had run a follow the law previously, but she had made this whole story up. It's just so happened that the person that she was describing happened to look like this guy now. According to Crowell, the police pressured her into identifying Dotson as her rapist, and she was still scared of telling the truth to anyone, so she went along with it. Dotson would end up being tried and convicted of rape and sent to prison, and Krowell would later recant her accusation. In five she said she was overcome with guilt about what she had done to him and that she had decided that it was enough was enough, she had to come forward and tell the truth. And prosecutors weren't too eager to do that. They I guess partly were worried that it was going to reflect really poorly on them. The trial had included testimony from various forensics experts, and it would mean that they were either fabricating evidence or very much misidentifying things, and that it was going to look terrible to them. So anyway, a judge ended up releasing Dotson on a one hundred thousand dollar bond, but Dotson wasn't truly exonerated until DNA tests in nineteen nine proved that he wasn't involved. So, in other words, his accuser had come back up and said, I made it all up. He didn't do anything to me. I was scared, and I came up with this story that I thought was going to help things. I did not intend for this to happen. And some of the legal community dismissed her statement. They said, oh, she's unstable, she's you can't rely upon her statements. And it wasn't until the DNA evidence came out that said Dodson could not have been the person that was accused of this crime because his DNA did not match the DNA that was gathered in the wake of her accusation. The whole story, by the way, goes into way more crazy detail and and there are a lot more twists and turns and a lot of tragedy involved in it as well. It's sad, it's an infuriating story. There's an excellent treatment of the story over at Northwestern University's Prints Care School of Law website. It has the title first DNA Exoneration. So if you want to read all about it, and it is an exhaustive account, uh, you should check that out, because it is fascinating as well as upsetting. The emergence of DNA led to the development of quality control guidelines for DNA labs and forensic investigators. It became clear that in order to make effective use of this information, of this knowledge of DNA, they had to make sure they created very straightforward, very uh standardized approaches to to reduce the possibility of destroying or altering evidence, either by accident or on purpose. You know, do something where you can document it step by step by steps so people can make certain that you did everything correctly, so that your conclusions can be seen as valid. Now, while these sciences, sciences and processes were developing, police forces and other law enforcement agencies were actually working to formalize the development and deployment of investigations. How do you teach investigators these these processes, Because a lot of them were developed independently, they are being made use in specific police forces, but they weren't necessarily shared. How did that come about? Well, in the nineteenth century, if you were in the eighteen hundreds and you were a forensic researcher, you were connected to some sort of law enforcement group, whether private or public. You were a auntly self taught. You got hold of whatever information you could find and you would study it or you would develop your own ideas in your own processes. It was very informal. One of the earliest formal schools in forensics was created by a guy named Rudolph Archibald Rice. He was a professor at the University of a Lausan, Switzerland. He had studied chemistry. At that university, he earned a doctorate in the field, and he began turning his scientific mind towards criminal investigation. He studied the discoveries of other criminologists, and in nineteen o nine he founded the Institute of Scientific Police. Other universities in Europe began to found their own forensic studies curricula, but then you had World War One and World War Two, and that wiped out a lot of those efforts. The Institute of Scientific Police survived the two World Wars because Switzerland was neutral in both of those. Today this school has a different name. It's called the School of Criminal Sciences. The same organization, new name, I mean, obviously updated with the more modern approaches. Rice in his time would actually publish a book about investigative techniques used in the event of burglaries and homicides, and he had planned future volumes to cover other types of crimes like counterfeiting, as well as other police matters like organizing a police force, but he ended up putting all of that on hold. The Serbian government requested his assistance to investigate war crimes committed by the armies of Austria Hungary during the Serbian War, and so he never finished those books. In An American named August Volmer, who was chief of police in Los Angeles, California, founded the first American police crime laboratory, which actually predated the FBI's crime lab by eight years. The FBI was formed in nineteen o eight, but it would not have its own crime lab till nineteen thirty two. It was the early nineteen thirties when colleges and universities began offering degrees in police sciences and minalistics, and in nineteen fifty the University of California at Berkeley created an early department of Criminology over in Chicago. Around that same time, academics founded the American Academy of Forensic Science, and today there are numerous colleges that offer coursework and forensic science. There are labs dedicated to the purpose of applying the scientific method when it comes to the investigation of crime, and there are companies that produce technology with the primary purpose of aiding in criminal investigations. And in our next episode, I will take a closer look at some of those actual technologies, some really cool ones, though they may not be exactly the same as what we see in television and film. That's it for this episode. 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