Holden Ford
Jonathan Groff's character, Holden Ford, is based heavily on Mind Hunter author John E. Douglas. The Brooklyn-born former FBI agent, now 72, went on to write a slew of other books on similar topics after spending years travelling around the country interviewing prolific serial killers and violent criminals like David Berkowitz, Ted Bundy, John Wayne Gacy, Charles Manson, Sara Jane Moore, James Earl Ray, Sirhan Sirhan, and Dennis Rader. Like Holden does in the show, Douglas also spoke to the Co-Ed Killer, Ed Kemper III. He interviewed him many times, later calling him one of the "brightest" inmates he had ever spoken with.
In addition to Mind Hunter, he penned the famed book Sexual Homicide: Patterns and Motives and later the Crime Classification Manual, both with Robert Ressler and Ann Burgess (aka the inspirations for Bill Tench and Dr. Wendy Carr). Douglas's work was so legendary that he was given two Thomas Jefferson Awards for academic excellence from the University of Virginia. He retired from the FBI in 1995 but has popped up on TV to discuss his career multiple times over the years.