Michael Leon Jones III, the Fairfax County man who has been charged with shooting an off-duty D.C. police officer, had been convicted of armed robbery four times before and was out on parole after serving seven years of a 28-year sentence at the time of the shooting, court records show.

The incident at the M Street Delly in Northwest Washington was the second time Jones had been charged with committing a violent crime while on parole, according to court records. He was a model prisoner during his most recent prison term and received time off for good behavior, prison officials said.

Jones' criminal record has sparked anew the debate among law enforcement and prison officials about how quickly criminals should be returned to the community from prisons often too crowded to hold them.

"I think it's absolutely scary," said Fairfax Prosecutor Robert F. Horan Jr. "I think the incident with Jones is just the tip of the iceberg."

"If the citizenry really wants to lock everybody up and throw away the key, fine," countered B. Norris Vassar, chairman of Virginia's parole board. "But I don't think that should be an uneducated decision."

Jones, 33, was paroled in July 1974 after serving two years of a five-year sentence for armed robberies of a bank, a convenience store and a grocery store, according to court records in Virginia and the District.

Four months after he was paroled, Jones was arrested and charged with shooting an Alexandria policeman during a liquor store holdup in which one man was killed and two wounded. Jones pleaded guilty to armed robbery in that case, and the shooting charge was dropped.

Jones served seven years of a 28-year, 8-month sentence for all four robberies in the James River Correctional Center near Richmond until he was paroled five months ago after receiving "excellent" reports from prison personnel.

"Everyone thought quite well of him and were convinced he had turned around," Vassar said. "He certainly suggested all the trappings for success."

Since that time, Jones has also been arrested and charged in the District with distribution of Dilaudid, a controlled substance. That case is pending.

Jones told police after his arrest in the shooting incident that he was working as a day laborer near the delicatessen and had planned the robbery because he needed to "get money to buy drugs," according to a police affidavit in the court file.

Also arrested and charged with armed robbery in that case was Herbert Lee Williams, 27, of Alexandria, who is being held in the D.C. jail. A third man, Maceo Millard Jones, 26, of Richmond, is also wanted on a charge of armed robbery in connection with the incident. The injured police officer, Robert B. Maring, 36, was reported in good condition yesterday at George Washington University Hospital.

Law enforcement officials argued that Michael Jones is symbolic of thousands of criminals who are released from prison early each year because legislators are reluctant to ask taxpayers for the authority to build new jails. On average, they said, parole rules governing what is called "good time" now keep first-time detainees in Virginia prisons an average of one-sixth of their assigned sentences.

"What they keep doing is passing laws and regulations to make the swinging door of justice swing faster," said Alexandria prosecutor John E. Kloch. "They are going to put ball bearings on it one of these days."

Virginia prison officials argued, however, that parole is necessary to maintain order in prisons and motivate good behavior. Vassar said it would cost the state several hundred million dollars for enough new prisons to house the 6,000 convicts who are paroled in Virginia each year.

"The indicators are that the rate of crime among those who serve their full sentences is three times greater than for those who are paroled," Vassar said.