The man accused of being the leader of an operation that forced a 16-year-old girl into prostitution and advertised her services on Craigslist said he knew the girl was underage because he had grown up with her.

Marcus Xavier Arrington, 21, appeared in U.S. District Court Friday morning at his change-of-plea hearing. Arrington pleaded guilty to one count of sex trafficking of a minor. He faces a possible life sentence, with a 10-year minimum, when a federal judge sentences him in January.

Four other defendants, three men and one woman, all in their early 20s, pleaded guilty earlier and are awaiting sentencing.

Arrington is the final defendant to plead guilty.

Honolulu police arrested the girl last month for prostitution. She told police a pimp had sexually assaulted her and forced her to work as a prostitute.

Arrington is awaiting trial in state court for kidnapping, sexual assault and promoting prostitution. He remains in custody unable to post $1 million bail.

Arrington and his co-defendants pleaded guilty to prostituting the girl in December 2008.

The girl told police Arrington forced her to work as a prostitute by plying her with drugs and threatening her with a handgun. She also told police he sexually assaulted her.