For years, the woman voluntarily handed over stacks of money made through prostitution to 52-year-old Stevon Warren. She placed the online ad on Craigslist, arranged the dates, negotiated the prices.

Did those circumstances mean he was her pimp?

Because she controlled every aspect of her prostitution business, Warren's attorneys argued in federal court this week that he wasn't. A Minneapolis jury said no dice Thursday when it found Warren guilty of sex trafficking after less than four hours of deliberation.

Prosecutors said Warren was the power behind the prostitution business, driving her to dates, taking most of the money she made, selling her drugs and controlling her life.

When Warren was arrested two years ago, Craigslist was a primary website for women offering sexual services and a bountiful target for investigators to cull juvenile and adult prostitution cases. Amid public pressure, the website shut down its adult services section last September, but that hasn't slowed down online prostitution, law enforcement says.

"Now we see new websites pop up all the time," said Sgt. John Bandemer, head of the Gerald Vick Human Trafficking Task Force. "We see the same girls posting an ad on four or five websites. It's nearly impossible to keep track."

The case against Warren was one of several online prostitution investigations by the Minneapolis Police Department's Violent Offender Task Force in the past few years. Officials said that the publicity from the cases immediately curtailed ads promoting sexual services, but that some slowly resurfaced.

One of the witnesses called by the U.S. attorney's office in Warren's trial was Clint Powell, Craigslist's head of customer service and law enforcement initiatives. Powell, who told Congress last year about actions Craigslist had taken to weed out and prevent adult services ads, was flown in from the company's headquarters in San Francisco. He discussed how the website tracked people who post ads. After his testimony, he said he has been asked only a few times to testify in a criminal trial.

Trying to recruit teen

Warren, of Woodbury, allegedly had been prostituting women for more than a decade when police received an anonymous tip about possible juvenile prostitution. In March 2009, an officer responded to an ad placed by a 23-year-old woman who later said Warren was her pimp. It said, "Hi, my name is Marissa. Cute, petite with high school looks." The woman, whose name isn't Marissa, and the officer met at a Minneapolis hotel. The officer said he was looking for a younger girl and was willing to pay $900 for both prostitutes.

The woman, who was in the throes of a long heroin addiction, said she could fulfill his request and called her 15-year-old sister. She testified this week about a deal she made with her sister that the 15-year-old would give the man a massage and arouse him and she would do the rest. The 15-year-old testified that she had never done anything like that and had resisted getting into the lifestyle of her sister and mother, who was also a prostitute.

The girl said Warren had twice previously asked if she wanted to prostitute herself and she adamantly refused. She even lied to a grand jury about what she and her sister discussed, she said, because she was embarrassed. Andrea George, one of Warren's two federal defenders, accused her of perjury.

The 23-year-old, who has been sober for 10 months, said most of the money she made was given to Warren. The remainder was used to buy drugs from him, she said.

He declined to testify.

Dueling arguments

Warren's attorneys argued that assistant U.S. attorney LeeAnn Bell never proved that Warren drove the woman to Wisconsin to meet a john several months before she was arrested by Minneapolis police, as the prosecution alleged. The john, who testified, said he was in the Twin Cities when he first called the woman after seeing her ad on Craigslist. They had sex and met up again a few months later at his home in River Falls, he testified. George offered phone records that she said showed Warren wasn't in Wisconsin at the time.

George also doubted Warren had any idea the woman's 15-year-old sister planned to do services with the undercover cop they believed was a john. In her closing statement, she said the 23-year-old woman spent her life being "a liar, cheater and manipulator" and told police Warren was her pimp because they were looking for the "man behind the scenes" when she was arrested. George said Warren had no ability to control her.

'It destroys their souls'

Bell countered that the case wasn't about control, but whether Warren participated in bringing the woman across state lines and having her juvenile sister engage in prostitution. (The girl did not engage in prostitution.)

"This woman wasn't making up a story," Bell said. "It's not a world people inhabit if they have other options."

The jury found Warren guilty of driving the woman across state lines to engage in prostitution and of sex trafficking of a minor.

Although the woman didn't say Warren physically coerced her to be a prostitute and hand over her money, pimps play mind games to control their actions, said Ann Quinn, a special agent with the state's Bureau of Criminal Apprehension who works with federal agencies on human trafficking cases. Some will find weak women to prey upon, and it's not unusual for a pimp to only see his prostitutes once a week to pick up money, Bandemer said.

It's not easy to get women to testify against their pimps, Quinn said in her phone interview. Many will remain friendly with the women in the hope they won't say anything to police.

"The whole subculture of prostitution is very dark and icky," she said. "It destroys their souls unless they get help."

David Chanen • 612-673-4465