A prosecutor told a state judicial disciplinary panel today that a prostitute had sex with Montgomery County Judge Henry J. Monahan twice last year in his chambers at the Rockville District Courthouse.

Darlene Ortte Shepard, a former prostitute and convicted drug user, said she charged Monahan $100 for each visit to his office in January and February 1994, the prosecutor said. She is expected to take the stand today.

Investigators from three agencies that reviewed the allegations against Monahan told the panel they were able to corroborate many of Shepard's statements.

Shepard led investigators through a private corridor of the courthouse to Monahan's office, suggesting she had been there before. And she provided prosecutors with a detailed description of the judge's genitals that Monahan initially verified but later said was incorrect.

Defense attorney William J. Rowan III attacked Shepard's credibility, noting her criminal record and the fact that she faced 47 years in jail and $30,000 in fines if she did not cooperate with authorities after her arrest on charges she stole credit cards out of handbags at a wedding.

"Judge Monahan categorically denies these allegations," Rowan said. "We state it did not happen. . . . The commission will have to judge the credibility of Judge Henry Monahan versus the credibility of Darlene Shepard."

The seven-member Maryland Commission on Judicial Disabilities will decide whether Monahan, 63, committed ethical violations that could warrant discipline ranging from a reprimand to removal from the bench. Monahan, the first Maryland judge to face a public disciplinary hearing, is accused of the prostitution incident and of refusing to evacuate a courtroom during a fire in 1993.

He was charged with violating ethical rules governing the integrity and independence of the judiciary, the avoidance of impropriety and the appearance of impropriety. The panel's findings will go to the state's highest tribunal, the Maryland Court of Appeals, for final action.

Shepard's brother, Fairfax County bail bondsman James Ortte, told the commission he called Montgomery police when he learned of his sister's intention to extort money from then-Assistant County Attorney Robert A. Jacques, a Shepard customer who had refused to pay her fee after having sex with her. Jacques lost his job after telling a newspaper reporter in September that he had sex with Shepard three times.

Commission prosecutor Christopher J. Romano said in his opening statement that Monahan met Shepard through Rockville defense attorney and former lobbyist Victor L. Crawford, who defended Shepard on a drug charge in 1989. Crawford and Shepard developed a personal relationship, and the lawyer kept her phone number in his office, Romano said.

"Victor Crawford provided Darlene Shepard's number to his friend of some 35 years, Judge Monahan," the prosecutor said.

Romano told the commission that Crawford told the Montgomery state's attorney's office in 1994 that he gave the number to Monahan at the judge's request.

"Somewhere in the winter, Monahan called for the number," Crawford was quoted in an investigative report read to the commission. "I never asked him why. If a judge wants a number on a hustler, that's his business."

But Crawford later denied knowing whether he gave Monahan the number, saying intensive chemotherapy and other drugs he was taking made it hard to distinguish between reality and hallucination.

"Maybe I dreamed it was . . . Monahan who called me," the lawyer said in sworn testimony taken in Montgomery because of his failing health. Romano said Crawford continued to practice law during that period.

Shepard's assertions were passed from the Montgomery County Police Department to the state's attorney's office and the office of the state prosecutor before finally reaching the commission.

At each level, Shepard persuaded investigators to press on with their case, Romano said.

Shepard drew detailed sketches showing what she described variously as moles, freckles or brown spots in Monahan's genital area.

Romano said the judge acknowledged having such "freckles in my groin area."

But Rowan said two doctors examined Monahan and found no evidence of the marks. Romano then presented a dermatologist who testified about how such lesions can be removed without a trace. CAPTION: Judge Henry J. Monahan leaves the court building after the second day of disciplinary hearings in Annapolis. Americans' Senior Center in Adams-Morgan, translates for Sara Klumer, 67, during news conference.