Creating a profile of a serial killer, is part science and part intuition. The science involves studying criminals who have committed similar crimes, to see what characteristics they all have in common. One common trait among serial killers, is a past history of abusing animals. In a search for the killer of two teenagers in Texas, a behavioral profile led to suspect Jason Massey � and hard science proved the profile was correct. Massey was executed by lethal injection on April 3, 2001.