Norman Barnes, already charged with kidnapping a 15-year-old Dorchester High School student and forcing her into prostitution at Boston-area motels, now faces charges he used a 16-year-old for the same purposes.

Indictments unsealed today charge Barnes with 10 counts of deriving support from a minor in prostitution, seven counts of aiding and abetting the commission of statutory rape, four counts of statutory rape, four counts of visual material of a child in a state of nudity and three counts of posing or exhibiting a child in a state of nudity, the Suffolk County District Attorney's office and the state Attorney General's office said.

Barnes, 28, with a record that already includes attempted murder and cocaine trafficking, has been held in lieu of $350,000 bail since May, when he was arrested outside a Quincy Best Western after he left the 15-year-old alone briefly and she used the time to go down to the lobby and contact her aunt online.

Authorites say Barnes used Backpage.com to sell the teens' services. At a Quincy District Court hearing in May, prosecutors charged Barnes gave the 15-year-old and a friend a lift home from Ruggles, only he refused to let the girl out and instead drove her to the Morrissey Boulevard Ramada Inn, where he told her they were now going to make some money - and showed her a folding knife.

Over the next two weeks, authorities said, Barnes moved the teen around different motels - and had sex with her himself in between selling her company on the Web site.

McSweeney said the teen and a friend were walking around the Ruggles Street area on May 9 when a guy stopped his Camry and began talking to the friend. The two then got in his car. He drove the friend home, but instead of driving the alleged victim home, told her to get into the front and drove her to the Ramada Inn on Morrissey Boulevard in Dorchester. "He made a comment they were going to make some money," McSweeney said, adding Barnes made sure to show the girl a folding knife he had.

Barnes is scheduled for arraignment on the new charges tomorrow in Suffolk Superior Court.

In a statement, District Attorney Dan Conley said:

This case makes plain that prostitution is not a victimless crime. We believe the evidence will prove that this defendant exploited two underage girls by photographing them in states of undress, advertising them online, and forcing them into sex with strangers. Cases like this don't reflect agreements between consenting adults -- they show the true form of human trafficking in Massachusetts.