A set of key court rulings and a guilty plea by a former bookkeeper to Medicaid fraud here last week have helped unjam a long-stalled grand jury investigation of Doctors' Hospital of Prince George's County and an affiliated nursing home, according to the Maryland attorney general's office.

In three harshly worded opinions that accused lawyers representing the hospital and nursing home and their owners and staff of using "diversionary strategems" and "ingenious obstructionism," the state's intermediate Court of Special Appeals overturned a Baltimore city court ruling that had barred the attorney general's Medicaid fraud control unit for more than a year from seizing hospital financial records and calling witnesses to testify before a grand jury here.

In another separate opinion, the Court of Appeals, the state's highest tribunal, ruled that the accountant-client privilege of confidentiality did not apply to keep the grand jury from subpoenaing various financial records of the hospital and nursing home operations.

Assistant Attorney General Stefan D. Cassella, who has headed the 2 1/2-year probe of the hospital and nursing home, called the rulings "extremely important."

Equally significant, in the view of Medicaid fraud unit investigators, a retired bookkeeper for the Magnolia Gardens Nursing Home adjacent to Doctors' Hospital in Lanham pleaded guilty last week in Baltimore city court to falsifying documents that she said helped the nursing home administrator and his wife divert nursing home income to their personal use.

The former bookkeeper, Norma R. Anders, said in an affidavit accompanying her guilty plea that administrator William R. Greco instructed her to pay for improvements to his newly acquired home in 1977 from nursing home accounts. She said Greco's wife, Doris, acquired various food items, including a "large quantity of shrimp," from the nursing home dietary department but never paid for it. Her affidavit added that some employes obtained food from the dietary department but reimbursed the nursing home.

The attorney general's office is seeking to determine the total value of the goods and services allegedly diverted by the Grecos, and possibly others. One source close to the investigation put the figure for the Grecos at $25,000 to $50,000 from 1976 to 1979.

Anders, 56, whose one-year jail sentence was suspended, has agreed to cooperate with the attorney general's investigation of Doctors' Hospital and Magnolia Gardens and is now expected to testify before the grand jury here.

The Medicaid fraud control unit's investigation of the 120-bed hospital and the 104-bed nursing home on Good Luck Road in Lanham began in August 1981. The two facilities are owned primarily by William Greco and Leon R. Levitsky, both medical doctors, and much of the facilities' income stems from state-paid Medicaid reimbursements.

Because the Maryland Department of Health and Mental Hygiene, which administers Medicaid programs in the state, is located in Baltimore, the Medicaid fraud unit went before a grand jury here, rather than in Prince George's County where the hospital and nursing home are located.

Once investigators began issuing subpoenas for documents and summonses for witnesses, a battery of nearly a dozen attorneys fought the action in a tangled series of legal maneuvers. They won initial rulings by Balitmore City Circuit Judge Milton Allen in February 1982 that the Baltimore subpoenas and summonses could not extend to Prince George's County and that records seized by state investigators at the hospital must be returned.

"That stopped the investigation dead in its tracks," Assistant Attorney General Cassella said in an interview.

Cassella appealed Allen's rulings. It resulted not only in this week's reversal of Allen and the renewal of the subpoenas and summonses by the Court of Special Appeals but also in a stinging rebuke by that court of the various lawyers involved in assisting the hospital and the nursing home.

"The effort of the attorney general to root out fraud in the medical assistance program of the State of Maryland has been thwarted, sidetracked, frustrated and delayed by an exasperating, though talented, 'full-court press,' " wrote Judge Charles E. Moylan Jr. for the court. Moylan was the author of all three opinions in the case.

Without naming him, Moylan said one lawyer displayed the "Byzantine cunning of a Medici" and at other times "assumed the studied incomprehension of the village simpleton."

At another point, Moylan said that every effort "to pin the attorneys down to what precise remedy they seek under what precise statute sees them scuttle off like a squid behind its cloud of ink . . . "

Several attorneys associated with the case refused to comment on Moylan's language or say if they will appeal the court's rulings. A secretary at Doctors' Hospital referred calls for Levitsky and Greco to their attorneys.