What's the Difference Between a Killer's Signature and M.O.?

iStock/fergregory
iStock/fergregory

True crime shows, documentaries, and podcasts are everywhere these days, not to mention all the crime-focused movies and TV shows—like NBC's Law & Order: SVU, CBS's CSI: Crime Scene Investigation, and Netflix's Mindhunter. And you've probably heard terms like signature and M.O. being thrown around a lot without much explanation as to what they mean, or how they're different.

If you're confused about the difference between them, well, you’re not alone. As former FBI agent and behavioral analyst John Douglas notes in his book Mindhunter: Inside the FBI's Elite Serial Crime Unit (which the Netflix series is based on), "Both [signature and modus operandi] are extremely important concepts in criminal investigations analysis, and I have spent many hours on witness stands of courtrooms throughout the country trying to get judges and juries to understand the distinction between them."

Douglas, who was recently in New York to promote his new book, The Killer Across the Table: Unlocking the Secrets of Serial Killers and Predators with the FBI's Original Mindhunter, out now, helped break down the difference between signature and M.O. for us.

M.O. stands for Modus Operandi, and, according to Douglas, it's a learned, dynamic behavior. "When a criminal starts perpetrating crimes, if something doesn't go right, he's got to perfect the M.O.," he tells Mental Floss. "He's got to get it better and better." In other words, unless an offender executes the perfect crime his first time out, he'll continue to tweak his M.O. as he goes. The method of committing the crime is modified for success. That's why, Douglas says, "you shouldn't link cases together strictly by modus operandi. … You don't do that because those characteristics could fit people that have nothing to do with the case as well."

But what you can use to link crimes together is an offender's signature, a term that Douglas says he coined. "A signature is a ritual—something [that] is done that is not necessary to perpetrate that particular crime," he says. "The signature is the ritual that is unique to the offender, and that's what you're looking for."

To demonstrate what he means, Douglas uses sports as an example. "It's like a baseball batter [who], before a ball comes in, does rituals," like touching his hat or cleats. "Or shooting a basketball: bounce it three times, [do a certain move], take the shot. It's not necessary to get it in the hoop or hit the ball, but in his mind he's got to do it. He's got to do it this way."

In Mindhunter, Douglas acknowledges that "the differences between M.O. and signature can be subtle." To demonstrate just how subtle, he compares two robbery cases. Both robbers made their captive undress; one "posed them in sexual positions, and took photographs of them" while the other did not take photos.

The latter made his hostages undress "so the eyewitnesses would be so preoccupied and embarrassed that they wouldn't be looking at him and so couldn't make a positive ID later on," Douglas writes. That's an example of M.O. The former robber is an example of a signature, because it wasn't something the offender had to do to rob the bank—and actually put him at risk of being caught, because he was in the bank longer. "It was something he clearly felt a need to do," Douglas writes.

Because the signature is unique to the offender, Douglas says that you can use it in trials: "A case in Washington state, the subject was posing the victims after he killed [them]. And all that was allowed for me to testify to."

There's one challenge with signatures, though. "You can only see it when it starts showing up in repetitive crimes," Douglas says. "You can't look at a single case and say, 'Oh, this was the signature.' Say the victim is posed—that may end up being the signature, but you've got to compare it to something, later on."

As criminology professor Scott A. Bonn, Ph.D., points out in a post for Psychology Today, "While every crime has an M.O., not all crimes have a signature." Now, whether you're listening to a true crime podcast or watching an episode of Mindhunter, you'll know the difference.

These Rugged Steel-Toe Boots Look and Feel Like Summer Sneakers

Indestructible Shoes
Indestructible Shoes

Thanks to new, high-tech materials, our favorite shoes are lighter and more comfortable than ever. Unfortunately, one thing most sneakers are not is durable. They can’t protect your feet from the rain, let alone heavy objects. Luckily, as their name implies, Indestructible Shoes has come up with a line of steel-toe boots that look and feel like regular sneakers.

Made to be incredibly strong but still lightweight, every pair of Indestructible Shoes has steel toes, skid-proof grips, and shock-absorption technology. But they don't look clunky or bulky, which makes them suitable whether you're going to work, the gym, or a family gathering.

The Hummer is Indestructible Shoes’s most well-rounded model. It features European steel toes to protect your feet, while the durable "flymesh" material wicks moisture to keep your feet feeling fresh. The insole features 3D arch support and extra padding in the heel cup. And the outsole features additional padding that distributes weight and helps your body withstand strain.

Indestructible Shoes Hummer.
The Hummer from Indestructible Shoes.
Indestructible Shoes

There’s also the Xciter, Indestructible Shoes’s latest design. The company prioritized comfort for this model, with the same steel toes as the Hummer, but with additional extra-large, no-slip outsoles capable of gripping even smooth, slippery surfaces—like, say, a boat deck. The upper is made of breathable moisture-wicking flymesh to help keep your feet dry in the rain or if you're wearing them on the water.

If you want a more breathable shoe for the peak summer months, there's the Ryder. This shoe is designed to be a stylish solution to the problem of sweaty feet, thanks to a breathable mesh that maximizes airflow and minimizes sweat and odor. Meanwhile, extra padding in the midsole will keep your feet protected.

You can get 44 percent off all styles if you order today.

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

The Reason Your Dog Follows You Everywhere

Crew, Unsplash
Crew, Unsplash

Depending on your mood, a dog that follows you everywhere can be annoying or adorable. The behavior is also confusing if you're not an expert on pet behavior. So what is it about the canine companions in our lives that makes them stick by our sides at all times?

Most experts agree on a few different reasons why some dogs are clingy around their owners. One is their pack mentality. Dogs may have been domesticated thousands of years ago, but they still consider themselves to be part of a group like their wild ancestors. When there are no other dogs around, their human family becomes their pack. According to Reader's Digest, this genetic instinct is also what motivates dogs to watch you closely and seek out your physical touch.

The second reason for the behavior has to do with the bond between you and your pet. As veterinarian Dr. Rachel Barrack told the American Kennel Club, puppies as old as 6 months can imprint on their human owners like they would their own mothers. Even older dogs will bond with the humans in their lives who show them care and affection. In these cases, a dog will shadow its owner because it sees them as an object of trust and security.

The last possible explanation for why your dog follows you has more to do with your treatment of them than their natural instincts. A popular training tactic is positive reinforcement—i.e. rewarding a dog with treats, pets, and praise when they perform positive behaviors. The point is to help your dog associate good behaviors with rewards, but after a while, they may start to associate your presence with rewards as well. That means if your dog is following you, they may be looking for treats or attention.

A clingy dog may be annoying, but it usually isn't a sign of a larger problem. If anything, it means your dog sees you in a positive light. So enjoy the extra companionship, and don't be afraid to close the door behind when you need some alone time.