The genre of “true crime” is growing in popularity in the form of documentaries and podcasts that cover real crimes pulled from news headlines in detail. There are also fictionalized movies and television series about true crimes. I am not especially interested in true crime, but it is the fictionalized narratives about real crimes that interest me least. Fictional crime stories are better—or have the potential to be better—than true crime stories. The difference between them can best be seen in two of director David Fincher’s films about serial killers: Se7en (1995) and Zodiac (2007).

To me, Se7en is the best serial killer movie ever made, with one of the greatest endings in cinematic history (which I will not spoil here). Zodiac, while a great movie, had a far less powerful ending. A true crime movie cannot* have a mind-blowing twist ending with poetic resonance like Se7en’s because the audience already knows what happened—assuming they’re familiar with the crime—which if it’s being adapted into a movie, it’s probably famous enough that most people know about it. (*Unless the director rewrites history entirely as Quentin Tarantino did in Inglorious Basterds, Django Unchained, and Once Upon a Time in Hollywood. But such films are a genre unto themselves.)

The Zodiac Killer is one of the most infamous serial killers of all time. He terrorized Northern California in the late-1960s, killing at least five people (possibly much more), and sent puzzles to newspapers to taunt the police, press, and public. The Zodiac Killer is also famous for having never been caught. Zodiac as a movie was quite good—some would say a masterpiece. However, the film’s impact was limited because we knew all along the detectives were never going to catch the killer or know with certitude who the Zodiac was—because in real life the case remains unsolved. That is what the movie was ultimately about—the obsession over an unsolved case, and how uncertainty and lack of closure can torment the mind and ruin one’s life. While I liked the movie, a deep-dive documentary about the same material might have been even better. True crime stories (and most stories based on true events) are usually best told in documentary form as opposed to fictionalized narratives. The prioritization of one (true story vs. good movie) inevitably comes at the expense of the other. You will either have to bend the facts to fit the narrative or weaken the narrative by adhering to the facts.

If you make a fictional movie about a serial killer, there should be a greater message—some reason to make it worth telling such a dark tale. But if it’s a true crime, based on real events, then there need not be any message. There are no moral lessons to be learned from most true crimes (other than “don’t do that”). True crimes are often just horrible things that mentally-ill people did for no good reason at all. It might still be worth it to learn what happened and why—but in that case you’d be better off watching a documentary that explains in detail exactly what happened with interviews from the actual people involved, rather than a dramatic re-creation that needs to be changed in order to make it more entertaining and/or make some kind of narrative sense. Real life doesn’t need to make sense, however; most often it does not. Murder is inherently senseless.

This is why fictional crime is superior to true crime in the realm of movies (and novels). The writer can use the fictional case of a crime and vicious killer in order to make sense of real crimes and vicious killers. It is the crime novelist’s job to find art and meaning in the vile mindlessness of murder. But to make true crime artful can be crass and fetishistic—which is the elephant in the room: People watch murder stories because they find them entertaining. There’s something grotesque about being enthralled by the murders of real people. But in a fictional crime story, you need not worry about that. There are no real victims, after all—they are just figments of a writer’s imagination.

Another problem with crime stories is that audiences often come to like and root for the villain, such as Hannibal Lecter. This is somewhat acceptable in the case of Hannibal because he is completely fictional, like Darth Vader. But if Hannibal Lecter was a real serial killer who ate real people, it would be highly objectionable for audiences to like him in any way. This has happened to a lesser degree with real-life serial killers portrayed on the big screen, such as Zac Efron playing Ted Bundy in Extremely Wicked, Shockingly Evil and Vile. Albeit Bundy was an exception among serial killers for having relatively good looks and charisma—but he was no Zac Efron.

In movies based on true crimes the writers and directors will invariably change things. This can cause issues because often the movie becomes more popular than the original story, so many people begin to believe that the way the crime is portrayed in the movie is the way it actually happened in real life. Most people’s knowledge of Bonnie and Clyde comes from the 1967 movie, which is not entirely accurate. Filmmakers will defend their decisions, claiming they had to change this or omit that for story reasons in order to make it work more dramatically as a movie. Which is fair enough. But that also proves my point—that reality and fiction are two separate things. True stories do not make good movies unless the story is altered.

Fiction works differently than real life; you need to edit reality to make it work as a narrative. This is where the phrase “Truth is stranger than fiction” stems. Audiences will not accept rare coincidences in fictional stories, but if that rare coincidence happened in real life then they have to accept it. Filmmakers may even need to change certain real events to make them seem more believable to the audience. Movie audiences will never believe this (event that actually happened) could actually happen… But then why bother using the true story as source material if you’re going to warp it so that it is no longer true? Too often the reason in Hollywood is simply to exploit the event as a money grab—to cash in on the popularity of the true crime. Audiences are more apt to pay to see a movie based on the famous Zodiac Killer than a movie about John Doe.

My point is not that there should never be movies based on true crimes. As I said, Zodiac was fantastic. Though Zodiac is an outlier among true crime stories because it is itself an examination of true crime stories. Fincher brilliantly captured the reality of true crime in a fictional movie about true crimes. By the end of Zodiac, the murders didn’t make sense, the bad guy wasn’t caught, and that senselessness, uncertainty, and lack of closure wreaked havoc on those individuals involved in the case—as true crimes often do in real life. There was no happy ending in the movie because there was no happy ending in real life—or any “ending” at all. The case remains unsolved to this day. Viewers of a fictional movie would be outraged by an ending like that. Ironically enough, some audience members were outraged by Zodiac‘s ending—or lack thereof. They wanted a fictional ending to the true crime.

People always have and always will love crime stories—myself included—and I don’t think that is necessarily a bad thing. There is a reason why we all desire to discover the darkest of crimes in society. It’s the same reason people are drawn to uncover conspiracy theories. Throughout most of our species’ history, when living in tribes of hunter-gatherers, if someone in the tribe was killed—whether by a fellow tribe member or an outsider—that was a potential threat to the rest of the tribe. Therefore everyone must find out who the killer was and stop them from killing anyone else again. Had humans not possessed a fascination with true crimes, they would not investigate peculiar killings, and the murderers would continue picking off victims without being caught until there was no tribe left. Hence humans with no interest in investigating odd deaths went extinct.

Our fascination with true crime is not just about justice, law and order, or entertainment—it is a deeply ingrained genetic trait beneficial to survival. Both true crime and fictional crime take advantage of or hijack humans’ innate evolutionary psychology. We cannot help but be captivated by a murder mystery—we need to know whodunnit and why. The odder the death, the more intrigued we become. Again, this is not necessarily a bad thing. It doesn’t mean we should stop telling dark crime stories. But when fictionalizing true crime, writers must be conscious of how they portray the crime and killer. Writers of fictional crimes must be conscious of this too, but without any real-life victims, they have the freedom to transcend true crime and infuse meaning into the madness. Fiction has the potential to turn the darkest aspects of humanity into illuminating art.