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Scott and Deanna Larson lay in bed unable to sleep, wondering where Bobbi was after she ditched yet another treatment center.

It was early July 2012 and they had thought their daughter was safely tucked inside Eau Claire Academy, a school and treatment center for at-risk youth in Wisconsin. But that evening, the phone rang and they learned she had run away again.

Feeling helpless, their thoughts raced. Was Bobbi hurting? Were people harming her? Would her drugged-out friends rob the Larsons' house, as they had done once before?

As usual, Bobbi had been reported missing to the authorities, but runaways didn't seem to be a priority. Teenagers run and teenagers come back, Scott was once told.

They began to hope Bobbi would get arrested on something minor, just so they would know she was safe.

As they dozed off, they kept a .40-caliber and a 9-millimeter handgun nearby just in case.

Even in Scott's most troubled imaginings, he didn't understand how quickly a runaway girl like Bobbi, with her ADHD and fetal alcohol problems, could be targeted by smooth-talking pimps or other predators. About a third of runaway teens, some advocacy groups maintain, will be approached within 48 hours on the street.

The mind of a pimp

Wearing a stylish pullover and cargo shorts, there was nothing to identify this man settling into a chair at a sidewalk cafe near the Mississippi as a pimp.

He was clean and friendly. Well-spoken. His only bling was a pair of diamond earrings. Modern-day pimps, he explained, do not look like gaudy pimps of the '80s. They look like nice guys. Like him.

A change of heart had caused him to stop pimping and start working with police, he explained, which meant he could not be identified. But he agreed to an interview. His daughters were growing up, he said, and he wanted to warn them away from guys like him. He swore he was remorseful about what he had done.

He ordered a Jameson and tossed a "hello" to a thin girl in her 20s as she walked by, bashful eyes peeking from under bobbed hair dyed bright pink. He was skilled at spotting girls like that, and that's what he was there to talk about: How pimps are deliberate masters at finding, tricking and enslaving vulnerable girls and young women into the sex trade.

Girls like Bobbi Larson.

"You look for someone who is, um …" he paused, searching for the right word. "Socially distant." He leaned back, satisfied at that description. "Someone who's wearing hip hop clothes, or wearing country clothes or raggedy, or wearing holey clothes. Her hair is matted. Her hair is dirty. … You can smell her."

Finding a girl to approach is easy, he said, scanning Minneapolis' cobbled Main Street. "From the suburbs they don't know the difference," he said. "I'm looking for the naïve daughter that you send back and forth to the bus stop."

He asked open-ended questions to figure out a girl's needs, then met them. If she wanted to get high, he offered drugs. He gave her affection, made her feel special and was reliable. All things a runaway teen like Bobbi might crave.

After showering attention on a girl, he carefully chose the right moment to suggest she help him out. "You put it up as, 'Hey look man, you're my woman, this is what we have to do to get money. You're not a ho,' " he said. " 'Baby … I need to buy us this car, get us this crib.' "

They were techniques used by many pimps, who moved from that conversation to taking photos of a girl in sexy lingerie and putting an ad on a website, such as Backpage.com, where people pay to post want ads for everything from selling furniture to hiring for jobs. An adult section peddles "escorts" and "body rubs."

It never took long before the phone started jangling with men eager to pay for sex.

"You really think about what you're actually putting [a girl] through. You're sending her in here and dealing with fat dudes, pedophiles, rapists, freaky dudes, nasty, you know."

Other pimps — those known as gorilla pimps — take a girl far away from home and everything she knows, then beat her if she resists working for him. "Next thing you know, she's completely loyal," he said.

But he preferred manipulating with attention, rather than intimidation.

It's a technique men used again and again with Bobbi Larson.

Descent into trafficking

Newly savvy about using dating websites to hitch rides, Bobbi said she posted a message in July 2012, offering $100 for a ride from the Eau Claire school for at-risk youth to the Twin Cities. She persuaded a friend to go with her.

She thought the man who offered the ride looked decent, but then convinced him to stop at a gas station after they saw he had duct tape and garbage bags in his car. Early that morning, they found another ride, from a man who looked nicer to them.

When they arrived in St. Paul, Bobbi told the driver they needed to use a cash machine to get the $100 to pay him. The girls ducked into an office tower with a U.S. Bank sign on it, but quickly left through a different door.

They found a ride to downtown Minneapolis from some men who dropped them off outside SexWorld, a store selling adult products and entertainment on Washington Avenue in the North Loop. Bobbi would later describe what she recalled happening next:

A man drove up, introduced himself as "E," and invited them to his hotel room. He was in his 30s, with a shaved head and slight beard. Bobbi thought he was handsome.

At the Red Roof Inn in Plymouth, E pulled out a bag of cocaine and put some on the hotel room counter, Bobbi said. She and her friend snorted some. Buzzing with the high, Bobbi remembered hearing E tell a friend that they should "try these girls out and see if they're even worth it."

Bobbi knew that meant they wanted sex. She wanted more of E's cocaine, so she worked hard to please him that night.

Later, she and her friend showered, got some food and watched TV — a reprieve of normalcy and luxury from life on the streets.

Soon E told the girls he wanted to help them get on their feet.

Bobbi told E she would need a credit card to post an ad online. He took them shopping for outfits at Citi Trends on E. Lake Street, she said. Then he took photos and gave them a credit card and his phone to post an ad on Backpage.com, according to court papers.

In 2011, 46 attorneys general, including Minnesota's Lori Swanson, signed a letter labeling Backpage.com a "hub" of child sex trafficking and calling its efforts to limit such ads "ineffective." Once owned by Village Voice Media, the parent company of City Pages in the Twin Cities, it was split off into an independent company last fall in the wake of the controversy.

Those posting adult ads there encounter a set of rules to which they must agree, including not posting material that exploits minors or assists in human trafficking. But anyone can click right through it.

An attorney for Backpage, Liz McDougall, explained that the company helps fight child sex trafficking through systems that include automated and human filters looking for illegal activity before ads are posted, and by reporting suspected activity and responding to subpoenas within 24 hours.

If Backpage discontinued adult ads, McDougall noted, children could be advertised on sites offshore that don't cooperate with U.S. authorities. She would not reveal how much revenue the adult ads generate, saying Backpage is a private company.

Ads with underage girls still slip through Backpage's safeguards. One of Bobbi's ads tempted customers with a "Special*Choose 1 or 2 girls** 1 girl is $150 and up." It listed the girls as "CHERRII AND PEACHES." Another showed a photo of them, hands linked. One listed Bobbi as "BABY" and touted: "I am open-minded, and love to have men satisfied." Another called her "HONEY" and showed a series of photographs; a "selfie" of her fully clothed, a "selfie" of her in bra and panties, and another of her backside in a thong.

When the phone rang, they answered and gave the men instructions to meet them at hotels where E would drive them — the Red Roof Inn in Woodbury, the Sandalwood hotel in Shakopee and the Northwood Inn in Bloomington, the girls would later tell police.

Many hotel workers around the country have learned how to spot sex trafficking in training spurred by Marilyn Carlson Nelson, then-chair of Carlson, a global travel and hospitality company based in Minnesota. In 2004, in her own company's hotel chains — including Radisson, Radisson Blu, and Country Inns and Suites — she launched a groundbreaking program to train employees to look for signs of suspicious activity and report it to authorities. Then she began lobbying other hotel chains to do the same and some followed suit.

But Bobbi and E managed to work in a variety of hotels in July 2012. Bobbi recalls E supplying her with a stream of cocaine. She wanted to get high before every trick, so she could feel numb, but he wouldn't allow it.

She lost track of how many customers paid to have sex with her over about two weeks that she was with E.

All kinds of men showed up at the hotels as she was trafficked, Bobbi recalled. Businessmen in suits. An older man who said he was a doctor. A blind man with a walking stick, who told her he had arrived there on a bus. Some men, wearing wedding rings, specified no scented lotions or baby oil because they didn't want to raise suspicions with their wives. Some reeked of body odor.

Men buy sex for all sorts of reasons. Some want to indulge in forbidden curiosities or sexual fantasies that a regular partner would reject. Some want sex without intimacy or commitment, researchers say. Some want intimacy with someone who likely wouldn't have sex with them otherwise. Some want to feel powerful over a subservient woman.

The legal risk for women in the sex trade has been greater than for men — although changing that has also been part of the statewide effort to redefine prostitution and how it is prosecuted.

Far more women than men have been arrested on prostitution-related charges in Minnesota during the last decade. But in recent years, federal and state prosecutors have shifted more attention toward going after pimps and customers in juvenile sex-trafficking cases. Minnesota prosecutors were filing cases in the single digits at the beginning of the past decade; they filed 59 cases in 2012.

In early 2011, Ramsey County Attorney John Choi enlisted prosecutors around the state to join him in a new approach to sex-trafficking cases, with the victim as the foremost concern. Even before the law changed, they voluntarily treated those under 18 as victims instead of criminals. Choi advocated helping victims work with authorities to pursue cases against their traffickers.

But he and other prosecutors know the dangers for girls and women being trafficked go far beyond the risk of arrest. Alberto Prece Palmer, a Woodbury man wanted in Georgia for attacking three women he met on Backpage.com, was arrested in March in the bludgeoning death of 18-year-old Brittany Clardy of St. Paul, who police say was advertising massage services on the website. Her body was found frozen in the family car in a Columbia Heights impound lot. Palmer also is suspected in the killing of Klaressa Cook, whose body was found stuffed in a car in a Minneapolis impound lot.

Leaving 'E'

Bobbi tried to make every encounter short and impersonal, like the business transaction it was. She had little time for small talk. She recalls just wanting to get it over with.

To a 17-year-old, all of the men seemed ancient and disgusting.

But the money felt good in her hands. She was surprised at how much cash her body could command. She handed her earnings over to E.

Toward the end of the second week, E became more controlling. He wanted her and her friend to earn more, at least $500 a night each, Bobbi recalled. Some nights, when they didn't make any money, Bobbi could see him grow angry.

But he wouldn't tolerate her getting upset. "I wouldn't dare to cry around him 'cause he would say 'You look weak right now.' " She learned to detach from her own emotions, and still remains stone-faced when describing it all.

"I may act tough," Bobbi explained. "I may look tough with my tattoos, but I'm not tough…. I mean, I can fight. I can put up a fight, but emotionally I'm just distraught."

E, whose real name is Broderick Boshay Robinson, 39, is in prison now, serving a 7½-year sentence after pleading guilty to promoting prostitution in Bobbi's case. Over the phone from the state prison in St. Cloud, he told a different version of events, saying he believed both girls were adults auditioning for jobs stripping at SexWorld. He wanted to help them with a place to stay and use of his iPhone, he said. They were paying him back for the hotels and for driving them places. He insisted he didn't know they were turning tricks. He maintained they left him to go with another man who had better drugs. He denied supplying them with cocaine. He has since appealed, arguing that he was misinformed and poorly represented.

Bobbi would later tell police they left E by telling him they were meeting a trick at the Snelling Motel in Minneapolis. Instead, she called a man who had been a customer and supplied them with heroin and cocaine. After E dropped them off at the motel, the other man gave them a ride out.

He said he was taking them to a house where they could stay in north Minneapolis. But first he had sex with Bobbi. Then, in the middle of the night, he pulled his car up to a one-story bungalow on Oliver Avenue.

A woman named Meranda Warborg let them in. She was 29 years old, her brown hair stylishly cropped short in back. Bobbi thought she was pretty.

Bobbi recalls being led to a bedroom toward the back of the small, cluttered house. A mattress had been flopped on the floor.

Warborg knew all about turning tricks. "The guy who brought us there, I guess he was a pimp," Bobbi concluded later. "I think the reason why I didn't catch on was just because I was so messed up."

Bobbi took most of a day off before turning tricks there, she would later tell police. She gave money to Warborg for using the house and to buy some crystal meth.

In the couple of days Bobbi stayed there, she didn't think of Warborg as a pimp, she said, but rather as someone in the same desperate situation of needing drugs and money.

On a bright summer Saturday at the end of July 2012, Warborg was walking toward her SUV parked out back when an unmarked Chevy Impala pulled up in front of the house.

Sgt. Grant Snyder stepped out.

One cop's metamorphosis

In all of his years on the Minneapolis police force, Snyder had asked almost every prostituted woman he encountered one question: Why did they do it?

Getting them to open up came easily for Snyder, a 51-year-old father of five who was as comfortable addressing crowds at sex-trafficking conferences as he was talking one-on-one with victims.

He knew even khaki pants could be intimidating, too business-like, to these girls and women. So he wore jeans and canvas sneakers. He complimented women on their choice of handbag. Sitting down at eye level, he spoke softly but quickly — so fast he had to occasionally pause to sneak a breath. Before victims knew it, he had them talking, too.

Snyder had taken a libertarian view of prostitution back in college, when he majored in human sexuality at the University of Minnesota: If women wanted to sell sex, why should the community stop them? Prostitution was ubiquitous in societies around the globe, he had learned.

But over the years, as he saw women and girls from all walks of life trapped in the sex business, he kept hearing the same three answers to his question about why they did it.

They were doing it only for the money.

They were trying to get out of it.

It made them feel "shitty."

The more he heard them talk, the more he saw their own disgust over having sex with strangers. Snyder began to see them as victims.

He also saw that the customers weren't the fringes-of-society men that most people imagined.

"It's the people that live down the street, that work down the hallway, that attend church where we do, that eat in the same restaurants we do, our kids play together," Snyder said. "It's shocking when you look at the demographic of who these guys are. They're married, educated, have families, have good jobs."

Once, on a sting, Snyder's fellow officer sympathized with the johns they were about to arrest. The guys had so much to lose: marriages, jobs, reputations, money.

That riled Snyder even more. For years, he said, society has treated prostituted women like dirt, stigmatizing their behavior but letting customers get off easy.

In 2009, as Snyder and other officers were busting a large sex-trafficking ring that dubbed itself "Minnesota Nice Guys," his attitude about prostitution changed permanently.

Prostituted women in the ring served about 30 high-income clients, roughly 40 to 65 years old, who had clean backgrounds and were considered trustworthy.

Snyder saw them differently.

"I saw that these were rich guys that were using vulnerable immigrant women … like playthings that they could buy," Snyder said. "These are men that are purchasing another person and they're getting them to do things they clearly don't want to do."

After they were caught, men in the case told police that they felt they were helping women who needed money.

"All that sort of entitlement bullshit — that I can do something that makes this OK," Snyder said. "There's a hypocrisy in all of that."

He came to believe that women and girls in prostitution, even those who said they were doing it voluntarily, were really doing it to survive, and they were damaged by it. It was a realization that would change his approach to policing. He would begin by immediately telling victims that he wasn't there to get them in trouble, that he wanted to make sure they were safe and that he wanted to help them.

Intent on extricating Bobbi from the system of trafficking, Snyder walked around the house toward Meranda Warborg.

Staff writer Glenn Howatt contributed to this report.

Read Part 3: One cop's determination

Go to Part 1: A teen's sex trafficking ordeal

Go to Part 4: Struggling to find a way forward