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.

From Green River Killer, Gary Leon Ridgway to Ted Bundy to Harold Shipman and more, experts on serial killers tell A&E True Crime who was the 'worst' serial killer and why.

In the wake of Golden State Killer suspect Joseph DeAngelo's arrest, A&E True Crime looks at some of the other high-profile serial killings, where the killer has stopped but currently still remains at large.

Psychologist Al Carlisle, who was part of a diagnostic team at Utah State Prison who evaluated Ted Bundy, talks about the serial killer's lonely childhood, participation in illegal activities at a young age and strong desire to control women, which Carlisle believes led to his psychopathic tendencies as an adult.

True-crime author Harold Schechter, author of 'Hell's Princess: The Mystery of Belle Gunness, Butcher of Men,' on what made serial killer Belle Gunness unique and if she tricked everyone into believing she died.

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.

Andrew Walsh, deputy chief of the Las Vegas Metropolitan Police Department, on how he used a mannequin as a decoy to catch a suspect in the murders of two homeless men.

Melissa Moore, daughter of Keith Jesperson, otherwise known as the Happy Face Killer, talks to A&E True Crime about what it was like as a child to learn her dad was a serial killer.

Wayne Williams has been in prison for almost 40 years after being convicted of murdering two men. Although he was never tried or convicted, the murders of 29 kids and young adults were attributed to him as well.

German serial killer nurse Niels Hoegel is suspected of killing more than 300 patients at two hospitals in Germany. Beatrice Yorker, an expert in serial killings in health arenas, tells us how killers in medical professions often get away with the crime.