How To Catch a Cheating Spouse, According to a Private Investigator

Suspecting a partner of cheating is a gut-wrenching feeling that leads many to seek professional help. But what exactly do private investigators do to catch a cheater?

The reality may be surprising. Private investigators (P.I.s) employ a range of techniques to uncover the truth, using everything from discreet surveillance to clever social engineering. Their methods can be as fascinating as they are effective.

Newsweek spoke to John Olsen, CEO of Salient Strategic LLC, a private investigations firm based in New York, about his tried-and-true methods for catching cheaters and what he sees most often in his work.

Infidelity is an issue that spans all walks of life. According to YouGov America research, 41 percent of men admit they’ve thought about cheating on their partners, while 28 percent of women confess the same.

Emotional affairs, too, blur the lines of fidelity: 74 percent of women consider sexting and nonsexual emotional relationships to be cheating, compared to 59 percent of men. Whether it’s a physical affair or an emotional one, these concerns often lead suspicious partners straight to the doorstep of a private investigator.

How P.I.s spot red flags

According to Olsen, several red flags often lead clients to seek his services. These include sudden changes in a partner’s behavior, such as becoming overly concerned about their appearance, unexplained absences or defensiveness around their phone.

“Some go as far as showering with their phone to keep it secure,” Olsen said. Sometimes, clients may already know something is wrong but need proof for personal or legal reasons.

Surveillance is at the heart of most infidelity investigations, he said. Private investigators follow the person suspected of cheating, documenting their activities without being detected. While this might seem straightforward, P.I.s need to get more creative than you might believe.

“If you think felony suspects are cautious, you should see a cheating spouse trying to cover their tracks,” Olsen said.

P.I.s don’t just follow their subjects; they build a profile, looking for patterns in behavior and movements using Open-Source Intelligence (OSINT)—publicly available data, like social media activity—to map out habits and routines.

Methods and Misconceptions

Olsen said that while he and other investigators rely on a few mainstay tactics, such as OSINT and surveillance, there’s no “one size fits all” solution. The most notable consistency in their work is a dogged willingness.

“We are willing to go places and do things that others aren’t,” he said. “I empower my team to use their creativity to devise solutions to our clients’ problems, as long as it is legal and ethical.”

There are plenty of misconceptions about the tactics private investigators use, especially in infidelity cases. Contrary to what some might believe, ethical P.I.s avoid illegal methods like wiretapping or using GPS trackers without consent. Though tempting to some clients for their speed and simplicity, these approaches can open the door to serious legal trouble.

Instead, Olsen said he and his team rely on legal methods such as surveillance and OSINT. Their goal is to gather evidence that holds up in court, should it come to that. While some clients might push for quick fixes, seasoned investigators know the importance of doing things by the book.

“Patience and ingenuity are what really matters here,” Olsen said.

In some cases, Olsen and his team will use “social engineering” techniques to place a P.I. in an ideal position for gathering information. While social engineering—manipulating people into doing specific actions or sharing confidential information—is most commonly attributed to scams and hackers, it can also be used to solve investigations.

Olsen said he and his team use the tactic sparingly and always within the law.

Real-Life Examples: ‘Not All Glamorous’

Olsen shared some cases he had recently worked on to illustrate how he and his team operate.

In one situation, Olsen was contacted by a woman who had just fired her housekeeper for stealing money and prescription drugs. Her husband was a golfer who would often take weekend trips away—and her alarm bells went off when, one day, he forgot his clubs but came home talking about how good his game was.

“The husband was ‘going out of state with friends to play,’ but our client smelled a rat. We followed him to the ‘game’—really a hotel just over the state line—and on the way, he stopped to pick up the former housekeeper. We sat on their hotel room, followed them to dinner, and more. Needless to say, they had a conversation when he returned.”

In another recent case, Olsen’s team went so far as to put a P.I. on the subject’s flight and place a team on the other side, ready to follow him when he landed. Another time, they have climbed small mountains for elevation to document someone’s presence at a house they were not supposed to be at.

Careful not to give “trade secrets” away, Olsen said, he concluded that he and his team “always find ways to do what [they] need to do. However, the nuts and bolts are not as sexy as people tend to believe.”

While movies and TV often portray P.I.s in a dramatic light, much of the work requires careful planning and quiet observation. It’s not all glamorous, Olsen said, but patience is key to gathering the needed evidence.

For many clients, turning to a P.I. is the last resort. Whether they need proof for legal reasons or just to confirm their suspicions, P.I.s bring closure by using ethical, creative methods. Infidelity investigations may not be as flashy as they’re portrayed in Hollywood, but they seem more inventive than we can imagine.