WALTHAM — Domestic violence charges against Boston Celtics forward Jared Sullinger were dismissed by a Waltham District Court judge today after Sullinger’s estranged girlfriend told authorities she would not testify against him.

Deann Smith, the woman whose accusations led to Sullinger’s arrest by Waltham police in August, had repeatedly asked for the criminal charges to be dismissed since the Aug. 31 incident between the couple in the home they then shared in Waltham. District Court Judge Gregory Flynn dismissed the charges today.

After the ruling, Sullinger declined to discuss the case. Asked how he was doing, Sullinger said, “Ready to play.”

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In paperwork filed by Sullinger’s attorney, Charles Rankin, the defense asked for the charges to be dropped, contending that there was no evidence to support the charges.

Rankin wrote that Smith, through her own attorney, has notified Middlesex District Attorney Marian T. Ryan’s office that she would invoke her Fifth Amendment right against self-incrimination if called as a prosecution witness.

Smith “will not appear and ... if she were forced to appear, she would invoke her 5th Amendment privilege against self-incrimination,” Rankin wrote. “Moreover, discovery in the case has revealed there are not excited utterances nor any other admissible evidence to support the charges.’’

In domestic violence cases, prosecutors can cite what a victim tells first responders — known legally as “excited utterances’’ — if victims refuse to testify later against their alleged abusers.

A spokeswoman for Ryan said the decision by Smith not to cooperate with law enforcement stripped prosecutors of the key evidence they needed to pursue charges against Sullinger.

“Where the victim is a necessary witness to the case, without her testimony, we cannot sustain our burden of proof,’’ MaryBeth Long said. “So the judge dismissed the case. We were not in a position to go forward.’’

Long said Smith’s decision to invoke her constitutional right against self-incrimination also undercut the case.

“There was an attorney who represented her, who said that she would assert this privilege,’’ Long said. “With that presented to the court, we were not in a position to go forward.’’

In a three-page affidavit, the attorney for Smith, Melinda Thompson, wrote that the couple argued on Aug. 31 in their Waltham apartment, and that Sullinger left for home in Ohio after their argument. Nine hours after the argument, according to the affidavit, Smith called Waltham police on their business line and reported the incident to police.

“Ms. Smith spoke with police and told them that she did not want to press charges against Mr. Sullinger,’’ the attorney said, describing the first contact between Smith and law enforcement. “She told them that she did not want to have him arrested. She also told police she did not want or need protection from Mr. Sullinger.’’

In the police report filed in court when Sullinger was arrested in September, police said Smith told them that she confronted Sullinger, whom she suspected of cheating on her. The two argued verbally, and the argument intensified when Smith started packing up her belongings, according to the report.

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

Smith and Sullinger began dating when both were students at Ohio State University and were living together at the time of the incident, according to records.

Smith has since moved back to Ohio, according to Thompson, her attorney.

“They certainly still talk. They definitely speak, and they’re on good terms,’’ said Thompson. “At this point, they don’t have plans to move back in together. To be honest I’m not sure about the status of the relationship.’’

Thompson would not offer an explanation as to why Smith called police nine hours after she argued with Sullinger. “I don’t want to get into the question of why she called police — because of her privacy,’’ Thompson said. “I don’t want to discuss the specific allegations.’’

Thompson said Smith is not critical of Waltham police for pursuing charges against Sullinger, even though she told them she was never in fear of him. “The police did their job,’' Thompson said.

Thompson said Smith wanted the case against Sullinger brought to an end.

“She wanted these charges dropped right away,” Thompson said. “I think it’s a good result for everyone. And I know Deann is happy to put this behind her.’’

Sullinger played just 45 games during his injury-shortened rookie season. But coming off back surgery, the bulky forward is expected to be an impact player for the Celtics this season. He will play major minutes, likely starting at either the power forward or center position.

The Ohio State standout is the Celtics’ best rebounder, but he has said that his conditioning is nowhere near where it needs to be.

Still, he was one of the Celtics’ most impressive players through training camp, and he averaged 10.1 points and 4.6 rebounds over 20.6 minutes in eight preseason games.