Gerald Frost, one of 12 inmates in the Prince George's County jail charged with sexual assault offenses after a 1982 Washington Post series, was acquitted yesterday by a Circuit Court jury.

Frost, 26, of Oxon Hill, stared straight ahead as the jury acquitted him of two counts of rape and one count of assault and battery. A rape conviction could have brought a life sentence.

At the time of the alleged rape Frost was in jail awaiting trial on a robbery charge. He was convicted on that charge and was released in June 1981.

The state's case against Frost suffered a major setback Wednesday when its key witness, Ronald Fridge, said that after four years he could not identify his attacker. According to the Sept. 26, 1982, article, Fridge, then 18, told Washington Post reporter Loretta Tofani that Frost had assisted another inmate in raping him. Fridge, who was released from the county jail after an acquittal a week after the rape, is now serving a seven-year sentence at the Delaware State Penitentiary for robbery.

Frost denied in his testimony Wednesday that he aided in the rape of Fridge.

Frost is the first of the 12 men charged with sexual offenses to be acquitted by a jury. In August 1983, sexual abuse charges against Clifton Earl Tucker Jr. were dropped when the alleged victim denied that he had ever been assaulted.

Frost's attorney, Frederick G. Seelman Jr., said after the acquittal, "The evidence in this case established a reasonable doubt in the minds of the jury. I don't think the evidence was there."

One juror who asked not to be identified concurred: "There was just not enough evidence in the trial to send a man to jail for life."