A D.C. Superior Court judge has ruled that it is more important to protect the anonymity of 264 methadone-using drug addicts at a city drug treatment clinic than to disclose their names to assist police and prosecutors in an investigation of a slaying.

Judge Frank E. Schwelb ruled recently that the patients' right to privacy overrode the U.S. attorney's office's need for the names in its probe of the still-unsolved slaying of a former patient at the clinic.

Government prosecutors argued that their investigation was virtually stalled because no witnesses could be found with information about the killing of William Kennedy, whose body was found Nov. 18 in the vicinity of the 'Train I' drug treatment clinic, 59 M St. NE.

While acknowledging that murder was the "ultimate crime," Schwelb said there still is a sufficient public interest in protecting the confidentiality of participants in the city's drug treatment programs, partly because of the high incidence of crime committed by drug addicts.

"Courts must therefore be both judicious and cautious in their approach to any action which has significant potential for undermining the rehabilitative goals" of the program against drug abuse, the judge said.

"It is undoubtedly the assurance that their anonymity will be preserved . . . that encourages many patients to join or remain in such a program," Schwelb said.

"Disclosure of the names of 264 [addicts] to law enforcement authorities might, in the long run, impair the fight against crime far more seriously than failure to apprehend Mr. Kennedy's murderer," Schwelb wrote in an opinion issued last month.

Police said that Kennedy, 29, of Landover, was found beaten to death. His body was recovered near the clinic, and police said the motive apparently was robbery.

Investigators located several witnesses who said they had seen Kennedy the previous day in front of the clinic, but were unable to locate any witnesses who had seen the killing or who could provide information about it.

As part of its investigation, the U.S. attorney's office asked the Alcohol and Drug Abuse Administration, run by the D.C. Department of Human Services (DHS), to turn over the name, address, and telephone number of each patient who had received treatment or had been present there on Nov. 17, the day before the body was found.

Attorneys for the agency, citing provisions of D.C. law that provide confidentiality for the patients, said that releasing the names would place the District's "entire narcotic treatment program . . . in jeopardy."

Turning over the names -- which numbered 264 on the day in question -- would break the city's "trust" with addicts who use the city's clinics, according to Holloway Wooten, a DHS official familiar with the case.

"You cannot go on a fishing expedition," said Wooten. "They could get the names, check their files, find that a person has a criminal record and end up busting him for drug use."

Although the city law provides that information can be turned over if a particular patient is the specific target of a criminal probe, there were no prime suspects in this case, according to Schwelb's opinion. The request was merely an attempt to locate suspects.

"Obviously we have our concerns about the privacy of individuals in drug treatment programs," U.S. Attorney Charles F. C. Ruff said this week. "We wouldn't have made the request if we had not thought the importance of the information outweighed those concerns." Prosecutors can appeal the judge's decision, but Ruff said no decision has been made whether to do so.

Schwelb also noted that he had tried to persuade city officials and the U.S. attorney's office to agree to a compromise, such as permitting clinic officials to interview patients and pass any fruitful information on to police. However, the prosecutors' office objected on grounds that the drug treatment personnel are not trained criminal investigators.

Schwelb also disagreed with government objections to a proposal that each patient be provided with notice and a hearing before his name was disclosed. The U.S. attorney's office had argued that if the patients were given such notice the killer might abscond.