At the moment, the question of whether Smith can be prosecuted hinges not on the attorneys’ salacious suggestions about Smith’s relationship with Copney but on the decision of a Superior Court judge.

The non-prosecution agreement that Smith signed in July 2009 states that the District Attorney’s office can declare the arrangement “null and void” in the event that “it is determined that [Smith’s] cooperation, assistance or testimony has not been complete, candid and truthful.”

Former prosecutors said that the D.A.’s office has the authority to revoke such an agreement in the event that a defendant is untruthful.

“When the Commonwealth goes the distance and says, ‘Okay, we’re not going to prosecute you,’ you have to do certain things,” said Karen A. Colucci, a defense lawyer and former Middlesex assistant district attorney.

Smith’s attorney contests prosecutors’ allegation that Smith broke that agreement, saying that the state’s case against Smith’s truthfulness rests on unreliable testimony provided by individuals involved in the crime.

“What is it that the government finds so unsatisfactory about Smith’s performance? ... On what basis?” Osler’s motion asks. “The government seeks to abrogate the non-prosecution agreement principally on the basis of isolated segments of the statements made by Jiggetts, Campbell, and Aquino.”

The decision is now in the court’s hands. Osler confirmed that the matter was discussed at a hearing earlier this month but said it is still under consideration.

“If she did in fact lie—if she gave false information knowingly, the court’s going to have to decide,” Colluci said. “They may nullify that agreement, and if they do so, she can be prosecuted.”

—Kerry M. Flynn, Hana N. Rouse, and Xi Yu contributed reporting to this article.

—Staff writer Julie M. Zauzmer can be reached at jzauzmer@college.harvard.edu.