The pregnant Maryland teacher shot dead and left in a shallow grave had tried to talk to another woman with whom her boyfriend was also engaged to marry, police said. Investigators lured the boyfriend, Tyler Tessier, into speaking at a news conference while Wallen was still missing with the hope that his demeanor and words would help them solve the mystery. Tessier, 32, was charged with the murder of Lauren Wallen, 31. Nancy Grace digs into this homicide with forensics expert Sheryl McCollum,  psychoanalyst Dr. Bethany Marshall, and CrimeOnline reporter Leigh Egan.