For the two D.C police special operations division officers, Richard Dassing and Robert Marring, it began as a routine traffic stop.

They had pulled over the driver of a van blocking traffic at Vermont Avenue and K Street NW one Tuesday night, and asked him for his license and registration.

He was Gary M. Colangelo, 20, of Sharon Hill, Pa. Again routinely, the officers radioed the police central dispatcher to make a computer check of the FBI's National Crime Information Center, to see if Colangelo was wanted for anything. The dispatcher punched Colangelo's name into a computer terminal. Moments later, the computer flashed back the code number 0999.

It was a "hit." The code said Colangelo was wanted in New York on a homicide charge.

But it turned out to be not as simple as that.

First, the code number was incomplete, D.C. police learned in the hours after Colangelo's arrest that he was wanted as a fugitive, not on a homicide charge, but on an attempted homicide charge. New York authorities said he had struck and injured his wife with a "drinking cup" in a Manhattan hotel room last August.

Second, D.C. police learned that authorities in New York were no longer that interested in Colangelo. The charge against him would probably be reduced to assault, they said, and the case would not be worth the expense and double of extradition.

By Wednesday afternoon, the fugitive charge against Colangelo had been dismissed in D.C. Superior Court, and Colangelo walked free from the courthouse.

It was the third time in as many weeks that New York law enforcement authorities had declined to seek extradition of suspects arrested on fugitive warrants in the District of Columbia.

The process has demoralized the D.C. police department's 13-member fugitive squad, according to the unit's chief, William McGill, and raised questions about the use and dependability of the national crime information retrieval system.

"There are always risks involved in arresting fugitives," McGill said, "so it's kind of a letdown when the other jurisdiction says they don't want the guy . . ."

The Colangelo case was especially galling, he said, because Colangelo had indicated he would waive extradition proceedings and return voluntarily.

"We have special difficulties with New York for some reason," McGill said. ". . . My men are now saying that if New York's not extraditing, we ought to have a policy here of not arresting their fugitives."

Leonard Rienzi, the Manhattan assistant district attorney assigned to the Colangelo case, said in a telephone interview that his office is in a "budget jam" and must be selective about costly extradition cases.

After reviewing the Colangelo case, he said, "The most we could make would be an assault case, and it was not worth the expense and trouble."

Extradition from Washington would require flying two detectives from New York to pick up prisoner and return him, plus food and possible lodging costs, Rienzi said.

"It could cost up to $1,000," he said, "and we'd probably end up with the judge giving him a $50 fine."

McGill questioned the $1,000 figure. Besides, he said, "attempted homicide is a very serious offense, and the person should be extradited."

McGill also contended that New York authorities should have "purged" Colengelo's name from the FBI's National Crime Information Center (NCIC) Computer if they had decided not to extradite him.

(NCIC, headquartered in Washington, maintains computerized files on wanted and missing persons, stolen autos and other property, and criminal histories on some individuals. Police agencies contribute data to NCIC and use it as a central information exchange point.)

Rienzi said he had notified New York police he was no longer pursuing Colangelo through NCIC, but the police apparently neglected to delete Colangelo's name because of the crush of paperwork. "You know, we handle 150,000 cases a year here," he said.

McGill said the coded NCLC reference to Colangelo was incomplete. "It had a '0999' for him which just means 'homicide' - anything from first-degree murder to involuntary manslaughter," McGill said. "They should have added a prefix to the '0999' to show the charge was attempted homicide."

The Supreme Court has ruled that an NCIC "hit," or discovery by police of a suspect through an NCIC computer check, is probable cause for an arrest.

"But if we keep having improper use of NCIC, like this New York case," McGill said, "the Supreme Court could very well reverse itself on this matter . . . It would be one hell of a wrench for law enforcement."