The government shutdown of Backpage.com this year sought to curtail the type of sex-for-sale classified ads that made the company infamous. Months later, though, the closure has prompted an increase in sex trafficking on San Francisco streets.

Reported crimes related to pimping and sex trafficking have more than tripled in 2018 — with 67 through August, up from 21 during the same period last year, according to police. Meanwhile, officers have made more arrests than previous years as much of the activity had been hidden online, said David Stevenson, a city police spokesman.

Violence against both sex workers and people soliciting sex is a concerning trend as well, said Sgt. Antonio Flores of the department's special victims and human trafficking unit.

"A few sex workers are becoming violent," he said. "Then there are those that tend to prey on sex workers."

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Backpage.com, long criticized by authorities for being an online brothel, was shut down in April after an FBI investigation, and CEO Carl Ferrer was charged with money laundering. The website's closure came after Congress passed laws that effectively made websites hosting adult ads responsible for the postings of users.

The new laws have had a side effect on San Francisco streets, said Pike Long, deputy director of St. James Infirmary, a peer-based health and safety clinic for sex workers in San Francisco.

"Without being able to advertise online," Long said, "a huge number of sex workers were forced to go outside, and many have reported that former pimps came out of the woodwork offering to 'manage' their business again since they were now rendered unable to find and screen clients online."

St. James saw a spike in street-based sex work in the month after Backpage.com was shut down, Long said, and screening clients has become more difficult because of the closure of other sites popular in the industry.

"The very bill that was supposed to stop trafficking has quite literally given formerly irrelevant traffickers new life," Long said.

Carol Leigh coined the term "sex workers" about 40 years ago and now advocates for them as director of Bayswan, the Bay Area Sex Worker Advocacy Network, in San Francisco. She said sex workers who are unable to advertise online or screen clientele are being forced into increasingly vulnerable circumstances.

"I hear from sex workers talking about suicide attempts," she said. "I hear about some considering working for exploitative 'managers' because of limited options."

By law, sex trafficking crimes are defined as situations in which a commercial sex act is induced by force, fraud or coercion, or in which the person induced to perform the act is underage.

Reducing sex trafficking through enforcement is difficult, Flores said, because it often requires a precarious buy-in by the victim. Police often struggle to get sex workers to testify against their traffickers in court, and many fear getting locked up or blacklisted in the industry.

In December, San Francisco police issued an internal bulletin to prioritize the safety of sex workers, who may ordinarily be subject to arrest, if they are the victims or witness sexual assault, human trafficking or other violent crimes. Since then, officers have been working to assure sex workers they will not be prosecuted if they come forward, Flores said.

"One sex worker didn't believe us at first," he said. "We had to show her the policy at the hospital."

Besides on the streets, sex work continues to thrive in hotels and massage parlors, Flores said. Social media platforms and dating sites like Sugardaddy.com and Lotsoffish.com are also used in the industry, he said. Getting trafficked minors off the street in these locations remains the top priority for police.

Flores said police had begun focusing more attention on online sex trafficking in recent years. "We saw things change — we were immediately getting different clientele," he said. "We were getting doctors, lawyers, IT guys. A lot of IT guys."

First-time offenders caught soliciting sex in San Francisco can avoid a trial by agreeing to go through a weekend police class that touches on issues such as the social implications of sexual addiction and the risks of disease and violence. A deal gone bad carries a real threat of robbery, assault and even death, Flores said.

"We have those reports," he said, "where not everybody has a happy ending."