Prosecutors in the case of a teen charged with statutory rape in connection with the suicide of a 15-year-old Massachusetts girl who was bullied acknowledged Friday that the girl’s birthdate wasn’t given to a grand jury that indicted the boy.

The teen’s attorney said he would ask again that the charge against him be dismissed.

In court documents, prosecutors said the only reference to Phoebe Prince’s age came from a police detective, who testified that Phoebe’s mother referred to her as 15 in a statement she gave to police shortly after her death. Prosecutors said that was enough for grand jurors to conclude Prince was underage when she allegedly had sexual contact with Austin Renaud.

“Although it would have been preferable for the grand jury to have learned the victim’s date of birth (which would have conclusively proven that she was fifteen at the time in question, and that, due to her untimely death, she never attained the age of sixteen), the evidence before the grand jury, and the reasonable inferences that could be drawn from it, was sufficient to establish the age element of the crime of statutory rape,”  Assistant District Attorney Thomas Townsend wrote in a filing opposing the defense motion to dismiss the charge.

Renaud’s lawyer, Terrence Dunphy, said the acknowledgement bolsters his argument that the grand jury did not have enough evidence to indict Renaud for statutory rape.

“They left the grand jury to speculate as to how old the girl was. They didn’t establish the element of age and so therefore they don’t have a statutory rape charge,” Dunphy said. “The indictment should be dismissed.”

First Assistant District Attorney Steven E. Gagne disputed Dunphy’s claim and said the grand jury had enough evidence to support the indictment.

“It is not necessary to inform a Grand Jury of a statutory rape victim’s date of birth, so long as the Grand Jury hears sufficient evidence from which they can conclude the victim was under 16 at the time of the alleged offense,” Gagne said in a statement.

Dunphy said Renaud denies having sex with Phoebe. He said a person he would not identify made a “single statement” that Renaud claimed to have had sex with Phoebe, but Dunphy said the assertion is not credible.

Prosecutors have said Phoebe, a recent Irish immigrant, was bullied relentlessly at South Hadley High school, on Facebook and through other electronic forums. She hanged herself in January 2010. Her death, one of several high-profile suicides, sparked national discussions about school bullying.

Five teens have been charged with criminal harassment and civil rights violations in the case. Renaud is charged with statutory rape, but is not charged with bullying Phoebe.