The special grand jury investigating rapes and sexual assaults in the Prince George's County Detention Center recently began asking jail officials and former jail officials about the policies of jail Director Arnett Gaston during the time the alleged rapes were occurring, sources close to the grand jury investigation said.

The grand jury was impaneled in September following a Washington Post series on rapes and sexual assaults in the jail in Upper Marlboro. So far, the grand jury has issued indictments against 12 men on charges of forcing, or attempting to force, fellow prisoners in the county jail to have sex with them.

According to sources, the grand jury asked four witnesses Thursday about Gaston's method of counting rapes at the jail, as well as about his management and security procedures for preventing rapes.

The witnesses were Capt. Gerald Rice, who still works at the jail, Rice's lawyer, Joseph Truhe Jr., James Carter, the jail's former director of security, and Carter's wife, Ann, formerly an executive assistant to Gaston.

The grand jury was told that Gaston did not count a rape or sexual assault as such in jail records unless the victim decided to press criminal charges against the rapists. As a result, the grand jury was told, jail records reflected fewer rapes and sexual assaults than actually were reported.

In the Post series, guards and inmates said sexual attacks occurred about a dozen times a week; Gaston estimated such incidents at less than 12 times a year.

Witnesses also told the grand jury that Gaston instructed certain jail officials to use their discretion in whether to write down such incidents, sources said. The result, witnesses said, was a low number of recorded sexual assaults in jail records.

Gaston could not be reached for comment yesterday, but told the Post last fall that he did not believe complaints of sexual assault unless the victim pressed charges.

Jail records on the number of rapes and other assaults are reviewed by the state Commission on Correctional Standards. The records also have been used by attorneys for inmates who brought a lawsuit against the jail, alleging overcrowding and poor conditions.

The grand jury was told that conditions at the jail encouraged rapes, and that guards who complained about the rapes and other poor conditions often were demoted. The grand jury did not ask witnesses about the roles of specific guards who were on duty at the time of the alleged rapes and sexual assaults being investigated, sources said.

However, one witness reportedly told the grand jury that a guard may have been directly responsible for a rape in December 1980 in the jail's cellblock left section. The guard, who still works at the jail, allegedly opened a cell for an inmate named Wallace (Bam Bam) Parker Jr. so that Parker could rape another inmate. The grand jury witness said that he did not see the incident himself, according to sources.

Special prosecutor Robert C. Bonsib, who is overseeing the grand jury's work, refused to comment on the focus of the grand jury probe. "You have been around long enough to know that I'm not going to say anything one way or the other about what the grand jury is or is not doing," Bonsib said.

In a related matter yesterday, Prince George's Circuit Court Judge William McCullough issued an injunction preventing jail director Gaston from assigning jail Capt. Rice to the midnight shift inside the jail. Rice and his lawyer argued that Gaston had assigned Rice to the midnight shift on Monday, five days after Rice was subpoenaed to testify before the grand jury. Rice's lawyer, Truhe, told the judge that Rice felt he had been given a message to behave on Thursday (the day the grand jury meets).

County attorney Ralph Grutzmacher told the court that Gaston's decision to assign Rice to the midnight shift was based on need and Grand Jury Ra that Rice's feeling that he had been given a message was speculation.