WALTHAM, Mass. – A judge on Monday dismissed domestic violence charges against Boston Celtics forward Jared Sullinger after his girlfriend said she would refuse to testify against him.

Sullinger, 21, pleaded not guilty last month to charges that included assault and battery and intimidation of a witness after his girlfriend, Deann Smith, told police he had repeatedly pinned her to a bed and the floor on Aug. 31 in the home they shared in Waltham.

A spokeswoman for Middlesex District Attorney Marian Ryan said Waltham District Court Judge Gregory Flynn granted a motion by Sullinger’s lawyer to drop the charges after Smith, through her own attorney, notified Ryan’s office that she would invoke her Fifth Amendment right against self-incrimination and would not testify as a witness in the case.

“She’s a necessary witness to the Commonwealth’s case, and without her testimony, we could not sustain our burden of proof,” said spokeswoman Stephanie Guyotte.

Sullinger’s attorney, Charles Rankin, did not return a call seeking comment.

Smith told police that Sullinger assaulted her after she accused him of cheating on her and began packing.

“During this heated argument in the bedroom, Jared pushed her down onto the bed and got on top of her,” Waltham police wrote in a report. “Deann states she tried several times to get up, but he kept pinning her down and would not let her up.”

The police report said Sullinger later threw Smith to the floor and wouldn’t let her up.

Sullinger averaged six points and almost six rebounds per game in 45 games as a rookie last season.

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