Buzz
Crime-related media, including shows, documentaries, and podcasts, are in abundance today. Add to that the crime-centric films and TV series like NBC's Law & Order: SVU, CBS's CSI: Crime Scene Investigation, and Netflix's Mindhunter. You've likely encountered terms like signature and M.O. used frequently, but the precise meaning and difference between them may remain unclear.
If you're unsure about how they differ, you're definitely not alone. As former FBI agent and behavioral analyst John Douglas points out in his book Mindhunter: Inside the FBI's Elite Serial Crime Unit (which inspired the Netflix series), "Both [signature and modus operandi] are critical concepts in criminal investigative analysis, and I've spent countless hours on witness stands in courtrooms across the country trying to make judges and juries understand the distinction between them."
Douglas, who recently visited New York to promote his latest book, The Killer Across the Table: Unlocking the Secrets of Serial Killers and Predators with the FBI's Original Mindhunter, now available, helped break down the distinction between signature and M.O. for us.
M.O. stands for Modus Operandi, and according to Douglas, it's a learned and evolving behavior. "When a criminal begins committing crimes, if something goes wrong, they need to refine the M.O.," he explains to Mytour. "They have to keep improving it." Essentially, unless an offender executes the perfect crime from the start, they will continually adjust their M.O. to increase their chances of success. This is why, as Douglas points out, "you shouldn't connect cases solely based on modus operandi. … Doing so might link cases that have no connection."
However, what you can use to connect crimes is the offender's signature, a term Douglas claims to have coined. "A signature is a ritual—something that is not necessary for the execution of the crime," he says. "The signature is the ritual unique to the offender, and that's what you're looking for."
To illustrate his point, Douglas uses sports as an analogy. "It's like a baseball player who performs certain rituals before a pitch is thrown," such as adjusting his hat or cleats. "Or a basketball player: bouncing the ball three times, performing a specific move, and then taking the shot. While these actions aren't needed to make the shot or hit the ball, the player feels compelled to do them. It's a necessary ritual in their mind."
In Mindhunter, Douglas acknowledges that "the differences between M.O. and signature can be subtle." To demonstrate just how subtle, he compares two robbery incidents. In both cases, the robbers made their captives undress; however, one "posed them in sexual positions and took photographs," while the other did not take any photos.
The latter robber made his victims undress "so that the witnesses would be so embarrassed and focused on the captives that they wouldn't be able to identify him later," Douglas writes. This is an example of M.O. The first robber, on the other hand, exemplifies a signature, because it wasn't necessary for the robbery itself—and actually increased his risk of being caught due to the extra time spent in the bank. "It was something he felt compelled to do," Douglas writes.
Since the signature is specific to the offender, Douglas explains that it can be used in court: "In a case in Washington state, the offender was posing the victims after killing them. That was all I was allowed to testify about," he says.
However, there is a challenge with signatures. "You can only identify it when it appears repeatedly in multiple crimes," Douglas states. "You can't look at a single case and say, 'Oh, this is the signature.' For instance, if the victim is posed, that might eventually be recognized as the signature, but it needs to be compared to other cases later on."
As criminology professor Scott A. Bonn, Ph.D., notes in a post for Psychology Today, "While every crime has an M.O., not all crimes have a signature." Now, whether you're tuning into a true crime podcast, searching for serial killer gifts, or watching an episode of Mindhunter, you'll be able to recognize the distinction.
This article was originally published in 2019 and updated in 2022.
