Mark of a Serial Killer

Three women found dead in the Seattle area had ties to the nightclub scene — and so did their killer.

The so-called "I-95 Killer" pursued gay men and placed items like leaves, socks, and sex toys in their mouths after their brutal murders.

Steven Brian Pennell, also known as the "Route 40 Killer," picked women up off the highway before torturing and killing them.

Several serial killers wouldn’t leave the scene of the crime without taking something — be it a body part or a piece of jewelry — from the victim.

Since the 1950s, hundreds of bodies have been found off America’s highway system, including most of the victims of the Colonial Parkway murders.

"Mark of a Killer" is looking back on the mementos and calling cards of some of the most horrific serial killers in U.S. history.

Serial killer Derrick Todd Lee was tied to seven brutal Louisiana murders through DNA evidence in 2003.

While speaking with investigators, Dennis Rader opened up about defining moments in his childhood that hinted at his future as the BTK serial killer.

Serial killer Randall Woodfield murdered at least seven people throughout his Interstate 5 crime spree, targeting victims from Northern California to Washington. 

Previously operating as the "Classified Ad Rapist," Bobby Joe Long went on to rape and murder at least eight women.