The D.C. Court of Appeals in an unprecedented ruling yesterday overturned the felony murder conviction of a Northeast Washington man on grounds that the 25 months that elapsed between his arrest and conviction by a jury violated his constitutional right to a speedy trial.

According to court authorities, the ruling by a three-judge appellate panel was the first of its kind in memory in the District involving an offense as serious as murder.

The defendant, 39-year-old Whitfield Graves, is currently serving a sentence of 20 years to life but is expected to be released within 21 days.

Graves was convicted two years ago on charges of felony murder, robbery and first degree burglary stemming from the 1979 slaying of James Robert Matthews, a reputed neighborhood bootlegger in Northeast.

The appeals court ordered that the murder indictment against Graves must be dismissed, meaning he can never be tried again for the crime.

The court opinion, written by retired Judge Catherine B. Kelly, held that prosecutors in the case had caused unnecessary delays in bringing Graves to trial and that Graves had been prejudiced by more than two years of waiting in D.C. Jail for his day in court.

Sources said that officials in the U.S. attorney's office were stunned by the ruling. U.S. Attorney Stanley S. Harris declined to comment, saying he had not received a copy of the opinion.

One high-ranking source in the office called the ruling "extraordinary," adding that Graves will become "a free man because the courts are clogged."

According to one official, the court rarely overturns any convictions on speedy trial grounds, usually not more than three or four times a year.

"I never thought I'd see the day," said Arthur Spitzer, director of the D.C. chapter of the American Civil Liberties Union.

"The D.C. Court of Appeals has paid lip service to the speedy trial requirements in the Constitution while upholding conviction after conviction. This is a welcome change," Spitzer said.

Frank Carter, director of the city's Public Defender Service, which represented Graves at his trial and on appeal, said yesterday he had not seen the opinion, but he commented that "this is a door we've continued to hammer at for a considerable time with mixed results."

Unlike the federal government and other Washington-area jurisdictions, the District of Columbia has no speedy trial requirement, although efforts by the ACLU and other groups to pass one have been under way for some time.

A defendant's right to a speedy trial has become an issue here as the local courts become bogged down in ever-increasing numbers of criminal cases, resulting in lengthy delays between arrest and trial.

According to a recent sample, felony cases are, on the average, 13 months old before they go to trial in D.C. Superior Court. Many defendants wait months, some more than a year, before they are ever tried.

In Maryland and Virginia, defendants must be brought to trial within 180 days of arraignment. Federal law limits delays in federal courts to 60 days.

Defense lawyers in the city frequently request that charges against their clients be dismissed because of long delays. But in nearly all cases, the appellate court has upheld convictions.

Yesterday's ruling was based on a Supreme Court decision that established guidelines for judging when constitutional rights to a speedy trial are violated.

Four criteria set by the court are the reasons for the delay, the seriousness of the crime, whether the defendant had asserted his right to a speedy trial, and whether he had been prejudiced by the delay.

Judge Kelly wrote that the court was "mindful of the gravity . . . of the crimes," but that Graves' "right to a speedy trial was intolerably denied" during months of court proceedings.

Judge John M. Ferren concurred in the majority opinion. Judge James A. Belson dissented, saying the reversal was inconsistent with a similar case in which the court upheld the jury's conviction.

According to the court, several months of delays were directly attributable to a government request to continue the case because police officers who were to be key witnesses were on leave and could not appear in court.

Another delay resulted when the prosecutor in the case tore ligaments in his knee and had to stay home.

The case was further delayed six months when the government appealed a lower court ruling that a confession Graves had given to police could not be used as evidence.

Graves was arrested along with two codefendants after Matthews' body was found bound and gagged in his home, where he sold liquor without a licence. According to prosecutors, Graves, along with Larry N. Brown and Alvin Postin, had agreed to rob Matthews.

Brown was convicted of strangling Matthews. Graves and Postin were convicted as aiders and abettors, each on a charge of murder.

Brown and Postin were convicted in trials held several months before Graves' trial. Brown was sentenced to 27 years to life in prison; Postin to 20 years to life.

Those convictions have been upheld by the appeals court.

Court sources said they expect that the U.S. attorney's office will ask that the ruling in Graves' case be heard by the full nine-member appellate court.