When I think private eye, I think of a tough-talking Humphrey Bogart playing Sam Spade. I think of sleuths, stakeouts, car chases and femme fatales.

But mild-mannered gumshoe Philip Becnel assures me the job is not that glamorous. The skill set is more akin to a reporter’s, requiring good writing, fact-gathering and a knack for getting people to talk.

Becnel, 38, founded and owns Arlington-based Dinolt Becnel & Wells Investigative Group, a boutique private-eye firm that earns a big chunk of its income evaluating people’s body language.

He’s not getting rich, but Becnel says the job has its moments, just as journalism occasionally does.

Take the case of the missing mattress, wherein a hotel manager who was fired for stealing a new mattress claimed she was sexually harassed.

Becnel was put on the case. His job was to interview Miss Mattress for an attorney who was thinking about taking her case. Her darting eyes and delayed answers gave Becnel doubts.

The body-language expert recommended the attorney pass on the case.

Then there was the philandering global Fortune 500 chief executive who was making nice with one of his vice presidents. The vice president wanted to sue after the affair cooled and she was demoted.

“We interviewed former employees who had left the company,” said Becnel, who worked for a law firm that was thinking about taking the vice president’s case. “They corroborated parts of her story” — like the executive’s penchant for sending her suggestive e-mails while she was making presentations. “I recommended they take the case,” the investigator said.

She got a settlement. The chief executive got a goodbye handshake from his employer.

Becnel, an entrepreneur who has written two books, earns $125,000 in a good year. That includes $50,000 or so in base salary, plus a bunch of the revenue from his share of interviews. Because he owns 100 percent of the company, he can keep any profits or roll them back into the business.

The six-person firm grosses around $500,000 in a good year. In 2010, it grossed $560,000 and closed the books with $90,000 in profits. But last year a law firm that owed him $27,000 went out of business, and Becnel’s firm incurred an annual loss of $7,000 on $460,000 in revenue.

Most of his business comes from plaintiff’s attorneys who represent clients who want to sue somebody. Because plaintiff’s attorneys generally don’t get paid unless they win, they need to know whether their would-be client is telling the truth — and whether it will stand up in court.

Most of Becnel’s clients arrive through word of mouth, although the firm has a Web site and is on Facebook and Twitter. New clients usually are asked to put up a retainer. Becnel’s payroll is just shy of $300,000, and rent is $30,000. He also pays $5,000 for liability insurance.

The George Mason University anthropology major didn’t set out to a private eye. He fell into it.

When a friend quit her job for a firm that performed court-appointed investigations for indigent clients, Becnel stepped in to fill her shoes. He picked up where the woman left off and started closing cases for $10 an hour.

He ventured into risky neighborhoods, tracking down the suspects or witnesses in drug cases and minor felonies. The firm’s owner eventually handed over the entire business to Becnel, who has a talent for getting people to chat.

“I’m unassuming, and that sort of Columbo effect played well for me,” he said. His interview technique involves keeping an open posture and looking people in the eyes in an open, friendly manner that conveys confidence and gets people to cooperate.

The aspiring novelist said another important skill is the ability to write compelling reports.

“My business is selling reports to clients,” he said. “That’s what it boils down to. They hire you on the basis of how good your reports are. If they are sloppy and don’t reflect what witnesses said, they are of no use. They should be flawless.”

Becnel said he concentrates on quotes because they must stand up in court. A witness may say one thing to an investigator but say something else in court, with a judge, jury and room full of onlookers present. The attorney must be able to refer to the interview in case the witness goes wobbly.

Becnel’s niche is reading someone’s body language and telling whether they are lying.

He is certified in the Reid Technique, which is behavior analysis that reads body language. It is commonly used in criminal cases, but Becnel’s aha moment was to use it in civil litigation, where he could warn a trial lawyer if his star witness — or even his would-be client — was lying.

He discovered behavior analysis while working on a big sexual harassment case for an employment firm. Attorneys for the plaintiffs had gone ahead with the case based on sworn depositions from a dozen women who said they had been propositioned for sex.

They may have had the witnesses, but a Montgomery County jury didn’t believe the plaintiff who was bringing the lawsuit. Becnel’s client lost the case — and nearly $100,000 in trial preparation went down the drain.

“Afterwards, I went to the lawyer and said, ‘Part of the reason you lost is they didn’t believe the woman.’ I said, ‘I could give you impressions of whether [witnesses] are telling the truth or not,’ ” essentially saving the attorney from going down that road again.

The interviews take two to three hours at $150 per hour, and Becnel performs an average of four interviews a week. The interviewer gets $29 an hour, and the rest goes to Becnel’s firm to cover salaries and overhead.

The cases typically involve workplace harassment, whistleblowing, sex abuse or wage and contract disputes. Private investigators licensed in Virginia must take a standard course, which costs about $500. Becnel said he is licensed to carry a gun in the state but rarely does so.

I asked Becnel about problems private investigators face. He said he has so far avoided one the most common traps: getting emotionally sucked into a case.

“You do a few cases and you realize that what you thought was a very strong case or very compelling case turned out to have another side of the story you didn’t see,” he said. “This is not advocacy. You have to take [people’s] stories with a grain of salt.”

He recommends that anyone getting into his business choose their partners carefully and hire an attorney to write a strong operating agreement among the partners. He did both.

“Picking the right business partner is as important as picking the right spouse,” said Becnel.

I thought Sam Spade was single.

Follow me on Twitter: @addedvalueth.