A federal jury convicted a Dorchester man Tuesday of sex trafficking involving a teenage girl, according to US Attorney Carmen M. Ortiz’s office.
Michael Gemma, 30, was convicted in US District Court in Boston of using force, fraud, and coercion to cause a minor to engage in prostitution, and transporting a minor across state lines for the purpose of prostitution, Ortiz’s office said in a statement.
The investigation had been ongoing since 2011, Ortiz’s office said. A state trooper stopped Gemma on Sept. 30, 2011, for speeding. He was accompanied by a teenage girl with no identification.
The trooper took custody of the 16-year-old girl, who said that Gemma had driven her to New York and New Jersey for prostitution, Ortiz’s office said.
Gemma was arrested and indicted in May 2012. The victim testified that Gemma and an accomplice took photos of her in lingerie, which they posted on Internet sites. The photos were used in advertisements that offered sex with the victim for a fee, according to Ortiz’s office.
The sex trafficking involved taking the victim and other young women to motels in Massachusetts, New York, and New Jersey, where customers were looking to pay for sex.
“Gemma and the other pimps would control the prostitutes by threatening them and, at times, beating them,” said Ortiz’s office.
Sentencing is scheduled for Sept. 9.
Gemma faces a minimum sentence of 15 years in prison and a maximum of a lifetime, five years of supervised release, a $250,000 fine, and restitution, according to the US attorney’s office.
Jennifer Smith can be reached at jennifer.smith@globe.com.