For Jeffrey Dahmer, it was watching certain movies. Dennis Rader, known as the BTK Killer, set the mood by pretending he was a spy. Ted Bundy liked drinking alcohol before some of his slayings. Not every serial killer has a signature routine, but some of them do engage in some sort of ritual or preparation before a killing.

Although cannibals have always existed throughout human history as a cure for overpopulation, a means of survival during a famine, or even a way to contend with grief, what's more rare are murderers who kill for sport and then devour their victims. We talk to Dr. Eric Hickey, a forensic psychologist, on why some killers eat their prey.

Dr. Mike Aamodt, forensic psychology professor at Radford University, on why female serial killers have declined over the years, why there was a big jump in serial killings in the U.S. between the 1960s and 1980s and his most surprising finding in his research of serial killers.

Serial killers often live fairly ordinary lives with normal employment, enabling them to blend in with colleagues. Their legitimate jobs also offer them one more key perk: an opportunity to help carry out or conceal their crimes, according to experts.

Why do so many killers—Jeffrey Dahmer, Ted Bundy and David Berkowitz to name a few—abuse animals before targeting people? An expert provides insights on how the two behaviors are linked.