For one day this week, it looked as if there would finally be an answer to a question that has dogged D.C. Mayor Marion Barry since 1987: What really happened that January day in Los Angeles when he collapsed and was rushed to the hospital, the day after the Super Bowl, the same day Washington was buried under a brutal snowstorm?

Did Barry really suffer a flare-up of a hiatal hernia, as he told reporters upon his return to the District?

On Wednesday, Barry's close friend Lloyd N. Moore Jr. was forceful in his testimony at Barry's drug possession and perjury trial. Moore, a Washington lawyer, said he had been told by A. Jeffrey Mitchell, who accompanied Barry on the trip, that Barry had been smoking "cocaine laced with something." Moore testified that Mitchell was so worried that medical personnel might uncover Barry's drug use that he barred the hospital from taking any blood tests.

Mystery solved? Not quite.

Yesterday, Mitchell, a prosecution witness who offered evidence of Barry's drug use at other times, had a different story for the jury: There were signs that the mayor might have used cocaine, but Mitchell said he did not know for sure. He said he was absolutely certain, however, that he had not told Moore that Barry had smoked cocaine.

To make things even murkier, defense attorney R. Kenneth Mundy elicited responses that supported Barry's original explanation for the collapse. Barry, Mitchell said in response to Mundy's question, had drunk at least four bottles of champagne and a bottle of cognac that day. As for his descriptions of Barry's sniffing and nose gestures -- motions that Mitchell said Barry had used other times after snorting cocaine -- could there be another explanation?

"Sniffing is also a common symptomatology of a cold, isn't it?" asked Mundy. "However warm it was in California, it was still wintertime, is that correct, elsewhere?"

"That's correct," Mitchell said.

Into it all came yet another account -- albeit secondhand and not under oath in the courtroom -- from Mitchell's disgruntled former business partner. Norman Beebe, who is embroiled in a bitter civil suit with Mitchell, said in an interview yesterday that Mitchell had told him that "during the Super Bowl weekend that he and Barry did nothing but cocaine for two days."

The incident itself is not crucial to the case. It is merely one of more than 100 incidents that prosecutors have elicited to prove that Barry was a regular cocaine user from 1984 to 1986 -- the thrust of the conspiracy charge. But the Jan. 26, 1987, collapse always has loomed large in the public consciousness.

While Barry was relaxing in California -- having a manicure at the Beverly Hills Hilton and playing tennis -- District residents were howling about the paralyzing two-day storm, which had dumped near-record amounts of snow, and the city's failure to get snowplows on the streets quickly.

Barry's explanation of his collapse at the time -- that drinking too much had caused recurrence of a hiatal hernia -- seemed to flare tempers even more. Just what was Barry doing in California while other Washingtonians could barely get out of their driveways?

In his testimony, Mitchell suggested that the only people who may ever really know what occurred are Barry and a couple of women who visited him shortly before his collapse. Mitchell said he did not know who the women were or what happened between Barry and them behind closed doors.

All he knew, Mitchell said, was that he and Barry had smoked some marijuana and drunk too much, and that Barry gave the appearance of having used cocaine after one of the women left. Whether Barry had used cocaine, he said, he could not be sure.

Mitchell said that after the last woman left, he next saw Barry sitting in the living room with his head back, clearing his nose and making grunting noises. He said Barry was sniffing heavily and pulling at his nose, a gesture Mitchell said he had seen Barry make "often after we had cocaine."

Barry, he said, looked uncomfortable and told Mitchell that he was having trouble breathing. When Barry's condition did not improve with a walk outside to the deck, Mitchell called Barry's security agents and an ambulance, he said.

At the hospital, Mitchell said, Barry was given oxygen and his condition improved markedly, so much so that Barry "wanted to leave at that point." Mitchell said Barry did not want to take any medical tests.

Mitchell's recollection of the event lacked the color, emotion or certainty of the secondhand descriptions provided by Moore and Beebe. Mitchell also took advantage of nearly every opportunity to dispute Moore's rendering of their conversation, often on key points.

For example, Mitchell testified that he never told Moore that he had attempted to bar the hospital from taking any medical tests or that he had direct knowledge of Barry's smoking cocaine. In fact, at several points during cross-examination, Mitchell appeared relieved to agree with Mundy's efforts to discredit Moore's account and acted more like a defense witness than one for the prosecution.

But almost as quickly as Mundy planted doubt, Assistant U.S. Attorney Judith E. Retchin resowed the same ground. For example, although Mitchell said he never told Moore about Barry's cocaine use in Los Angeles, Retchin reminded Mitchell that he had told the grand jury in April that he had.

At the end of the examination, Mundy suggested to Mitchell that if what he said was true, would it not be natural as a good friend to ask Barry if he had been using cocaine "if you wanted to get him medical help, right?"

"Well, it could be," Mitchell responded.

But Retchin had the last question: "Sir, why did you not ask why Mr. Barry had been using cocaine?"

"Because I probably in my unprofessional and unscientific manner thought he had," said Mitchell.