The former governor of Michigan, Rick Snyder (R), was hit with criminal charges last week over his role in the drinking water contamination crisis in the town of Flint. He is fighting the case and his attorneys say the charges are "wholly without merit."

Will this usher in a new era where elected officials could be thrown in prison if an environmental catastrophe occurs on their watch? Not likely, says Bob Percival, a law professor at the University of Maryland who leads the school's environmental law program. We spoke to Percival about why prosecutions like Snyder's are so rare for our weekly environmental podcast, Parts Per Billion.