Criminal profilers, like Douglas or the team on Criminal Minds, use their knowledge of common serial killer traits to try and get in the mind of the unknown subject (or the unsub, for short) that they're looking to catch. In truth, the real FBI's Behavioral Analysis Unit investigates crimes other than purely serial killers, but Douglas was instrumental in its creation as one of the earliest psychological criminal profilers. He's written several books on his work, including Mindhunter: Inside the FBI's Elite Serial Crime Unit, and Inside the Mind of BTK.
When Mandy Patinkin left Criminal Minds, the character of Gideon was replaced by David Rossi (Joe Mantegna). Rossi, though, also takes some inspiration from Douglas. Both characters are senior members of the BAU who have been there from the beginning.
They aren't the only ones. According to A&E Real Crime, Douglas was also the inspiration behind the character Jack Crawford in Silence of the Lambs, as well as the premise of the Netflix series Mindhunter, which follows two FBI agents as they interview serial killers.
However, just as Douglas amazingly got the detail about the stutter correct, he missed the mark on the killer's age. Criminal profilers have had success stories that paint them as psychics, but they've thrown out just as many details that didn't pan out. Though Criminal Minds portrays the behavioral work as crucial to each case's success, there's plenty of criticism against real profiling. Still, it makes for endlessly entertaining TV.
