Montgomery County District Judge Henry J. Monahan had an uncommon form of amnesia caused by a stroke when he tried to break into a private residence here early one morning last spring, his attorney said today.

Following that incident, Monahan was arrested by Hagerstown police and charged with the kind of misdemeanors that often come before him in court -- breaking and entering and assault and battery.

Monahan's attorney, James J. Cromwell, said in opening arguments in his trial in Washington County District Court that the defendant was the victim of a small brain-stem stroke, which cut the blood supply to his temporal lobe and caused "transient global amnesia."

As a result, Monahan "isn't responsible for what happened . . . . He had no control over his actions," Cromwell said before retired Judge Edward O. Thomas, who was brought in to hear the case.

Three Hagerstown police officers testified today that Monahan was apprehended at about 2:30 a.m. on May 3 at a home near the Holiday Inn, where he was staying during an annual jurists conference.

The officers said Monahan identified himself at various times as Judge Lawrence Rodowsky, Judge John Corderman and Gov. Harry Hughes. Patrolmen Thomas Alexander and William King said that Monahan slapped one of them, tried to pull the badges from their jackets and repeatedly cursed them. The officers testified that they believed that Monahan was intoxicated.

According to hospital records introduced at the trial, Monahan was found to have a blood alcohol level of .22 percent. A level of .13 percent or above is grounds for a charge of intoxication, Maryland state police said.

Since his arrest, Monahan, 52, has been assigned to administrative duties.

Today he took the stand and testified for nearly an hour, speaking in a clear voice and responding "Yes, sir" and "No, sir" to questions.

Monahan testified that at about 6:30 p.m. on May 2 he went to the conference hospitality suite in the hotel and had one Scotch and soda. He took a second drink to sip on the bus that was transporting judges to a cocktail party at a Hagerstown home, he said. He said he had a third drink at that party, which preceded dinner back at the hotel.

Monahan's memory fades at that point, he said.

Monahan's other attorney, William J. Rowan III, said that the judge is believed to have had a stroke about the time of the dinner, based on a loss of memory at that point.

In affidavits filed in the case today, other judges gave these accounts of Monahan's actions:

*Monahan was "going from table to table kissing the hands of different people" at the dinner, said Circuit Court Judge Lloyd L. Simpkins of Somerset County. "He even kissed the back of my hand," Simpkins said.

*Monahan went to Robert C. Murphy, chief judge of the Court of Appeals of Maryland, crouched down by his chair and said, "Bob Murphy, I want you to account for your Catholicism," Murphy's affidavit.

*Monahan went with other judges to a nearby hotel after the dinner, according to Montgomery County Circuit Judge William M. Cave. While others danced, Monahan sipped drinks from the glasses of others and apparently knocked a bowl of pretzels on the floor, Cave said.

The other judges saw Monahan to his room at about 1:10 a.m. At about 2 a.m., Hagerstown police responded to the break-in report.

When he learned at the hospital of the events of the preceding night, he told the court today, "I couldn't believe it. I had been arrested. I wanted the earth to open and swallow me up. I had never had anything like this happen."