As far as endings go, the curious case of Marvin Harrison left something to be desired.

District Attorney Lynne Abraham announced yesterday that she would not file charges against the NFL star for shooting last April 29 in North Philadelphia.

Abraham said prosecutors could not "vouch for the credibility" of any of the people who gave police a total of nine accounts of the shooting.

She detailed "untrustworthy and sometimes false" statements made by Harrison; Dwight Dixon, the alleged victim who filed a civil lawsuit against Harrison in September; Robert Nixon, another man who claimed he had been wounded in the incident; Malcolm Poindexter, whose 2-year-old son was injured by shattered glass; and Stanley McCray, who works for Harrison.

Ballistics evidence proved that at least five shots had been fired from Harrison's Belgian-made handgun at 25th and Thompson streets on that spring day, but Abraham said investigators could not prove who had fired the weapon.

Abraham did not exactly clear Harrison's name. In fact, she suggested that criminal charges could be filed down the road, after Dixon's civil suit plays out.

"I'm pretty comfortable that I know who fired the gun, but I'm not going to say because I don't have the evidence," she said.

Abraham's announcement stunned Robert Gamburg, the attorney who's representing Dixon's civil suit against the Indianapolis Colts wide receiver.

"It's mind-boggling," Gamburg said. "I can name 15 district attorneys who would have been more than willing to go to court with the evidence they had and present the case."

Opting not to file criminal charges because of credibility issues "would eliminate about 85 percent of the murder prosecutions in the city of Philadelphia," Gamburg added.

Abraham's announcement disappointed some in law enforcement. "We feel like they're just afraid someone will come in here and make them look silly," said a police source who worked on the case.

"Nothing is ever a sure thing when you go to trial, but that doesn't mean you back off," the source said.

Harrison's agent, Tom Condon, did not return calls from the Daily News. In a statement, Colts president Bill Polian said: "We are pleased with this development and defer to her [Abraham's] ability to weigh the actual evidence."

Investigators do believe that Harrison, 36, and Dixon, 32, had been at odds after a dispute that started at Harrison's bar, Playmakers, at 28th and Cambridge streets, two weeks before the shooting.

Abraham said McCray, Harrison's employee, told police that Dixon was carrying a gun when the dispute escalated on the day of the shooting. Abraham noted that police had never found a weapon that could be traced to Dixon, who previously served time for a 2000 drug conviction.

Harrison admitted to getting into a fistfight with Dixon that day in front of a hot-dog stand down the block from the ga- rage he owns on Thompson Street.

He claimed that he had heard shots being fired after Dixon left. Harrison also told police that his gun was in his suburban home the day of shooting, and claimed he had never fired the weapon.

But detectives found the gun in Harrison's North Philadelphia garage a day after the shooting, and crime-scene investigators recovered at least five slugs at the crime scene that were later proved to have been fired from Harrison's unique gun.

"We're always told that ballistic evidence is proven to a scientific certainty. What happened to that?" Gamburg said.

"It [the gun] can't be at Harrison's suburban home and at 25th and Thompson at the same time," Abraham noted. "And it can't not have been fired and fired, so who's going to be the witness? How do I prove my case? With these witnesses? I don't think so."

Dixon showed up at Lankenau Hospital in Wynnewood later that night, nursing a gunshot wound to his left hand.

Initially, he told police that he had been shot while he resisted a robbery at 63rd Street and Lebanon Avenue in West Philadelphia. But police became suspicious when they found his bullet-riddled truck at 38th and Market streets, Abraham said.

The following day, Dixon changed his story and claimed that he had been shot by two men at 25th and Thompson. Eventually, police sources said, Dixon told investigators that Harrison had shot him.

Two people who could have theoretically added weight to Dixon's account were of little help to investigators.

Poindexter, whose son, Nasir, was injured just a few feet away from the shooting, refused to speak with police. And Robert Nixon - who at first claimed he also was shot during the incident - admitted to having made his account of the shooting, Abraham said.

Gamburg said he will push ahead with the civil suit, and plans to bring police detectives, Dixon and Harrison in for depositions.

Depending on the statements they all make under oath, "a criminal prosecution may yet be possible," Abraham said. *