Mindhunter Season 2 is, among other things, a rotating door of the 70's most notable serial killers. Holden and Bill sit down with William Henry Hance, The Son of Sam Killer, and Charles Manson, among others. While William "Junior" Pierce may not be as infamous as some of the other killers featured in the series, Mindhunter still puts the same effort into recreating Pierce to an eerily realistic degree, much like they did with Ed Kemper and the many other killers featured in Season 1. Mindhunter even used photos of the real William Pierce to fully flesh out the character and provide some insight on what the man valued — primarily, snacks.
William Pierce doesn't take up much room in Season 2's narrative, serving only to provide a dead-end on Holden's hunt for the BTK Killer and to introduce the young FBI agent to Atlanta. In fact, Pierce isn't mentioned in Mindhunter: Inside the FBI's Elite Serial Crime Unit, suggesting that the BSU's meeting with him was fabricated (or just left out of the show's source material). While Pierce's conversation with the BSU may not have been true to life, the character's love of snacks absolutely was.
During the interview, Pierce stuffs his face with Mallomars in exchange for discussing his crimes. Later, Holden's temporary partner in Atlanta, Jim Barney, explains that he got the idea to feed him snacks from a picture of Pierce of his bed covered in snacks, likening his prison cell to a 7-11 convenience store.
The picture shown in the series is an actual image of Pierce, his jail cot holding sliced bread, ice cream, cigarettes, and much more.
Listen, Pierce's crimes — murdering and raping an estimated nine women and men in the span of a year — are not funny at all. But this attention to the mundane details is what makes Mindhunter so much fun to watch for true crime buffs. During the interview, when he's not chowing down on sweets, Pierce stumbles over his words and pronounces "fancy" of words in either a thick dialect or just completely wrong, all while explaining that he is a genius.
Pierce recalls a time where he lashed out at someone for calling him a "moron" — a sentiment that Holden repeats in the car later following the conversation. While the show portrays Pierce as being someone from an impoverished background and lacking a formal education, how he talked in real life is the subject of speculation as no publicly available video or recording exists of Pierce.
While it's difficult to determine just how realistic Mindhunter's depiction of Pierce is, the show proves just how much value they put on research by taking one picture of Pierce's bunk and spinning that detail out into a crucial plot element of the character's limited time on the show.
While Pierce may not be as prominently featured as David Berkowitz or Charles Manson, the show's depiction of Pierce is a great example of the show's willingness to make all of their serial killers feel frighteningly realistic.