Mindhunter has returned for season 2, bringing with it more real life serial killers and tragic true stories. The Netflix series stars Jonathan Groff as Agent Holden Ford, who works in the FBI’s Behavioral Science unit alongside Agent Bill Tench (Holt McCallany) and Dr. Wendy Carr (Anna Torv), developing a database of serial killers to try and find common profiles and patterns. And what better way to find out how serial killers think than by sitting down with the killers who have been caught and asking them about their crimes.

Created by Joe Penhall and executive produced by David Fincher, Mindhunter is based on a book of the same name by the real-life Holden Ford: former FBI agent John E. Douglas. Together with his colleagues at the BSU, Douglas conducted interviews with some of America’s most notorious serial killers - from Jeffrey Dahmer to Ted Bundy - in an effort to develop better ways to identify and apprehend killers who were still at large.

In Mindhunter season 2, Holden and Bill become involved in an ongoing high-profile case: the Atlanta child murders. However, as they try to put what they’ve learned into practice, they encounter resistance from a justice system that’s entrenched in old-fashioned police procedure and fraught with politics. Here’s how much of Mindhunter season 2 matches the true story, and how much is fiction.

The True Story of Mindhunter’s Behavioral Science Unit

The FBI’s Behavioral Science Unit was established in 1972, as a small team with just ten agents. Several years later, BSU Agents John E. Douglas and Robert Ressler (upon whom Holden Ford and Bill Tench are based, respectively) began the work of interviewing imprisoned serial killers and asking them questions about their life before they began killing, how they chose their victims, and their behavior after they began killing. In a 2018 talk at Boston College, Douglas said that Ann Burgess (upon whom Wendy Carr is based) had conducted a heart attack study to find out the factors that make it more likely for men to get heart attacks. “I saw this as a reverse-engineering type of thing,” Douglas explained. “Our illness is the offender, so we’ve got to backtrack… We’ve got to talk to the experts, and the experts are these guys sitting around in prison.”

As seen in season 1 of Mindhunter, the FBI was at first skeptical about the worth of interviewing criminals, but the BSU’s project garnered enough interest to attract significant funding. By 1979, Douglas and Ressler had completed their database of serial offenders and begun to implement what they had learned in the field - most notably consulting on the Atlanta child murders, as depicted in Mindhunter season 2.

Mindhunter’s Crime Details and Serial Killers Are Mostly Accurate

While Mindhunter is a dramatized account of the BSU’s work, where the show is most accurate and true to real life is in the nitty-gritty details of its serial murder cases and the interviews that Holden and the team conduct. For example, in season 2 Holden and Bill have the opportunity to interview notorious murder cult leader Charles Manson (Damon Herriman), and are warned not to make him feel self-conscious about his 5'4" stature. Manson begins the interview by clambering up onto a chair and sitting on the back of it, looming over Holden and Bill. This is exactly what Manson did when John Douglas went to interview him. “He sat up on top of the chair to dominate me, to look down on me,” Douglas recalled. “But I let him do it because I don’t really care, I’m just trying to get information out of this character.” Bill’s favorite party anecdote, about Manson asking for Holden’s sunglasses and then bragging about having stolen them, also happened in the real interview.

However, for those who are hoping to listen to some of the BSU’s interviews with serial killers, there’s bad news: almost none of the interviews were actually taped. “I only used a tape one time,” Douglas said. “Because when you’re dealing with a prison-type situation, the trust is not there.” Any attempt to tape the interviews would make the subjects paranoid, and in fact Douglas and Ressler didn’t even take notes during the interviews in order to avoid putting the interview subjects on edge. Instead, he and Ressler would assemble basic notes before the interview and fill out their notes about the interview afterwards.

When it comes to the details of the killers’ crimes, Mindhunter sticks almost entirely to the facts. Wayne Williams, the prime suspect in the Atlanta child murders, was indeed stopped after a police officer heard a splash in a river that Williams had just driven over. As in the show, there wasn’t enough evidence to hold him at the time, but Williams was eventually arrested and convicted of the murders of two adults. In Mindhunter season 2, Holden’s “instinct” that Williams is the killer they’re looking for earns him criticism from the district attorney and Holden’s colleagues. Something similar happened in the real story; when asked by a reporter what he thought of Williams as a suspect, Douglas replied that “he looked good” and that “if he panned out, he’d probably be good for at least several of the cases.” This earned Douglas a letter of censure from the Bureau for speaking inappropriately about an ongoing case.

The BSU’s Personal Lives Are (Mostly) Fictional

Where Mindhunter takes the most creative liberties is with the personal lives of its three main characters. Though Holden, Bill, and Wendy are based on real people, more than just their names have been changed, and in fact their personal storylines are almost entirely fictional. Bill is based on John E. Douglas’ colleague Roger Ressler, who did have a son, but not a son who witnessed the murder of a toddler and then suggested the dead child should be crucified. Though there have been a few well-known cases of older children killing toddlers, the exact scenario presented in Mindhunter season 2 appears to be pure invention.

Similarly, while Dr. Wendy Carr is based on a real-life BSU consultant Ann Burgess, the drama of her relationship with Kay in season 2 is fictional. Burgess herself is not a lesbian, and she was a consultant for the BSU rather than a full-time employee working at Quantico, like Wendy is in the show. Burgess also didn’t go out to interview the serial killers herself, like Wendy does in Mindhunter season 2, and she was a forensic nurse rather than a psychologist. However, Burgess notes in an interview with Pacific Standard, that Mindhunter is accurate when it comes to what kind of role she played within the BSU: “The show was right that I wanted them to be systematic so they wouldn’t get a lot of criticism from pure methodologists - they were certainly not researchers.”

Mindhunter’s approach of sticking to the truth when it comes to actual serial killer cases and getting creative when it comes to the main characters’ personal lives works well in season 2 of the show. In particular, Bill Tench being pulled between his work and the crisis at home is a compelling point of tension throughout the series that leads to an inevitable but nonetheless devastating blow in the season finale. It will be interesting to see how the fictional aspects of Mindhunter continue to work with the fact-based storylines in season 3.

More: What To Expect From Mindhunter Season 3