D.C. Mayor Marion Barry, seeking leniency in sentencing by a federal court judge, acknowledged yesterday that he is "a drug addict" whose past behavior was "degrading and outrageous."

In a letter to U.S. District Judge Thomas Penfield Jackson, who is to sentence him today on a cocaine possession conviction, Barry said he is "deeply sorry," and requested that he be sentenced to probation and community service.

"I had hoped to leave only a legacy of leadership in human and civil rights," Barry wrote. "Instead, because of my actions, I must also live with the personal pain and shame that cannot be erased."

The tone of Barry's two-page letter was a departure from his expressions of vindication immediately after the trial -- in which he was convicted on one count and acquitted of another, with the jury unable to reach verdicts on 12 others -- and his previous public insistence that he was addicted only to alcohol and prescription drugs.

Barry's letter was part of a voluminous filing at U.S. District Court here by his attorney, R. Kenneth Mundy, hours after U.S. Attorney Jay B. Stephens submitted a 19-page memorandum asking that Barry be sentenced to prison for a year, the maximum penalty.

Stephens urged Jackson to consider in his sentence evidence that Barry committed crimes for which he was not convicted. Prosecutors commonly make such requests.

Stephens wrote that Barry was guilty of the 12 cocaine possession and perjury offenses on which the jury deadlocked and suggested that he also was guilty of the one cocaine possession count on which he was acquitted.

"In short, the defendant is not genuinely remorseful about his criminality," the memorandum said. "He is sorry only that he got caught."

In his letter, Barry said he may have masked his real feelings about the case.

"When I sat in your courtroom each day," Barry wrote to Jackson, "hearing things about myself that I had not wanted to face, I may have appeared to be calm and unmoved, but on the inside, I was suffering nearly unbearable humiliation and deepest regret."

Along with Barry's letter to Jackson, Mundy submitted eight others, including one from Barry's wife, Effi; another from Benjamin L. Hooks, executive director of the NAACP; and a third from City Administrator Carol B. Thompson.

In asking Jackson to sentence the mayor to community service, Mundy suggested that Barry perform eight to 10 hours of volunteer work per week for a year. Mundy said two local agencies had agreed to accept the mayor.

One is Southeast Neighborhood House, where Mundy said Barry could work as a reading tutor or in its youth job program.

The other facility Mundy recommended is a city agency, the Cedar Knoll Youth Center. It is the city's main detention facility for juvenile offenders, run by the D.C. Department of Human Services. It is now known as the Oak Hill Annex. Mundy said Barry could work there as a tutor.

Barry, addressing one of the prosecution's main arguments for enhancing his sentence, said that "one of my greatest shames is that my behavior hurt, confused and disappointed young people, the very youth I have fought so hard to help and uplift. I was once one of those aspiring youth proud of my heritage."

In her letter, Effi Barry pleaded with the judge for leniency.

"I beseech you to search your humanity," she said. "What further punishment does this man deserve? For certain, there can be no greater sentence than to have the whole world tune into your day in court as you are publicly castrated.

"Must there be further abuse of {a} man, who because of his medically diagnosed alcoholism, became a pawn of those whom he mistakenly accepted as his close friends or confidantes and became vulnerable to the temptations they provided?"

She also questioned the truthfulness of some of the government's witnesses at trial.

"To my amazement, I heard the witnesses describe a person that sounded like a stranger to me," she wrote. "My assessment is that some of the witnesses for the prosecution raised more question and doubt in my mind than provided truth and accuracy to significantly substantiate the charges brought against my husband."

Under the federal sentencing guidelines, all offenses are rated in seriousness between 1 and 43, with treason at 43. Cocaine possession rates a 6. Conviction on that charge, under the guidelines, normally means a sentence ranging from probation to six months.

The 6 would be increased to 8 -- and the corresponding sentencing range could be increased to between two and eight months -- if Jackson is convinced by the prosecutors that Barry was guilty of obstructing justice by lying to a grand jury in December 1988 about his knowledge of drug use by former D.C. employee Charles Lewis.

If Jackson also concluded that Barry's conduct constituted an "abuse of the public trust," that could justify raising the offense level another two points, to 10. That calls for a sentence of six months to a year.

Stephens's sentencing memorandum urges that Jackson give Barry the maximum one-year prison sentence, and even suggested the possibility of an "upward departure" from the guidelines.

Under the guidelines, two points may be shaved off the count system if a convicted person accepts responsibility for his conduct. But Stephens argued that Barry continues to deny the full extent of his drug use.

The prosecution's memo revealed that Barry, in a post-conviction interview with probation officer Arthur Carrington, acknowledged far more drug use than was previously known. Carrington's pre-sentencing report, which is not made public, says that Barry admitted cocaine possession on two dozen occasions other than the one for which he was convicted, Stephens's memo said.

Barry, Stephens said, told Carrington he "usually used drugs no more than once a month."

Stephens said Barry was "not genuinely remorseful" in acknowledging his drug use and "obviously engaged in a thinly-veiled attempt to gain the court's sympathy at the time of sentencing." The admissions were full of "disclaimers that are flatly contradicted by the evidence" and greatly understated the extent of Barry's criminal conduct, Stephens said.

During the trial, the government produced witnesses who testified that Barry used drugs hundreds of times, sometimes a number of times in a given day.

Stephens's memorandum also cited Barry's "brazen" conduct during trial. "For example," the document said, "during the trial the defendant wore yellow boutonnieres and publicly referred to witnesses for the government as 'singing canaries,' demonstrating his scorn and derision for those who were testifying simply because they were testifying, and not necessarily because of any dispute with the substance of the testimony."

Barry also tried to lie in order to remove a potential juror he didn't like, Stephens said.

He was referring to a potential juror who was a teacher St. Albans School, the school attended by the mayor's son, Christopher. During jury selection, the juror stated that he would prefer not to serve because he thought it might be unfair for Christopher to see one of his teachers sitting in judgment of his father.

Later, however, the prospective juror told Jackson that circumstances had changed, because the mayor and his wife, Effi, were withdrawing Christopher from the school. At that point, Stephens's memo states, Barry "interjected falsely" that he and his wife had made no decision about that. When Jackson told his clerk to call the school to check, the memo said, Barry said that Christopher was indeed withdrawing from the school.

Effi Barry asked the judge to consider the effects of any period of incarceration on Chistopher: "For certain, it would only serve as a further stab to the heart of a little boy who has so valiantly stood tall through all of this ordeal, and has constantly said, 'My Daddy is a good man,' as so many around him have laughed and called his father bad."

In asking Jackson to allow Barry to do volunteer work, Mundy reminded the judge that other public officials convicted of more serious crimes had not been sent to jail. In particular, Mundy mentioned Michael Deaver, a former top aide to President Reagan, convicted of perjury, a felony.

Mundy also said that the mayor had been "punished enough."

"Whether deserved or not, he has been maligned, reviled and subjected to a constant barrage of innuendo," Mundy wrote.

Besides Effi Barry, Carol Thompson and Hooks, other people who wrote letters to Jackson on Barry's behalf were the Rev. Raymond B. Kemp, a former D.C. school board member and pastor at Holy Comforter-St. Cyprians Catholic Church; David H. Eaton, a former school board president and formerly Barry's minister at All Souls Church, Unitarian; H. Beecher Hicks Jr., Barry's current minister at Metropolitan Baptist Church; longtime Barry friend Ella McCall-Haygan; and Rev. Thomas A. Masters, a minister at a Florida church visited by the mayor while he was in a West Palm Beach drug treatment program.

Hooks called himself Barry's "mentor," and asked Jackson to deliver a sentence that "heals rather than destroys."

Hicks said that Barry is undergoing a sincere spiritual rebirth, and that Barry's joining his church around the time of the trial "was not a staged or cavalier act on his part."