THE CRIME: it is at once the most prosaic and the most terrifying of crime stories, an innocent victim blown away for no reason by a complete stranger. Whether it's at an airport at Tel Aviv or an apartment building on the West Side of Chicago, such an act has become a commonplace in our time. Lennon's murder apparently fits into one of the crime's best- known subdivisions - murder at the hands of a mentally sick, but formerly non- criminal, stranger.

The story of this crime is wretchedly simple. Shortly before 11 p.m. on Monday, December 8, John Lennon was shot four times in the upper back and shoulder at close range as he was entering the gateway of the Dakota, his home for the last seven years. Rushed to Roosevelt Hospital in a police car, he was pronounced dead on arrival. In fact, Dr. Elliot M. Gross, the city's chief medical examiner, said that death must have come within moments after the bullets struck. Officers at the scene arrested one Mark David Chapman, 25, of Honolulu, who allegedly made self- incriminating statements to the arresting officers and who bought the alleged murder weapon, a.38-caliber revolver, late in October at a Honolulu gun shop.

The next day, Chapman was arraigned in Manhattan Criminal Court on charges of second- degree murder and criminal possession of a handgun. The defendant entered no plea, for his court- appointed attorney, Herbert J. Adlerberg, recommended that his client be given a psychiatric examination to determine whether he is competent to stand trial. The judge agreed, and Chapman was remanded to Bellevue Hospital's prison ward for observation and tests. The next court hearing was scheduled for January 6, 1981.

This story, with a different victim and a different setting, would barely have made the metro briefs of any newspaper in the country. But the address was one of Manhattan's best, and the victim one of the most famous and beloved men in the world. Loved to death, as it turned out.

In the aftermath, the investigative and legal proceedings were carried out with dispatch. Even before the Phoenix could get a reporter to New York on Tuesday, the NYPD had pronounced its official role in the case at an end. At that point, the legal parties involved - the Manhattan district attorney and the defense - appeared agreed that the case of New York v. Chapman should proceed as quickly as possible. There seemed to be no reason for delay.

It is the fame and extraordinary talent of the victim that have made this murder unique, but it's worth examining the features that make the case so horrible, its banalities. Both the suspect and the weapon are the worst of cliches, horrible because we are so used to them.

The suspect: Mark David Chapman, Beatles fan, Christian, former security guard, would- be artist, well- liked guy. Described by the New York police as a 11 real wacko" and by attorney Adlerberg as "nuttier than a fruitcake," the veteran of two suicide attempts, Chapman appears to be a classic example of that late- 20th- century phenomenon, the "nice" person who collapses under the pressures of his life. Suicide didn't work, but it may be that murder did; Chapman is now far beyond any of the stresses of his past life.

"Most of me didn't want to do it, but a little part of me did," he is alleged to have told detectives. Which could serve as the confession for every "he was such a nice, quiet kid" murderer who ever lived. And more and more of them are appearing among us, from John Wayne Gacy to David Berkowitz to - well, check the suspect in the next big homicide in Boston. One radio reporter described Chapman as "more complex than at first believed." There is every indication that Chapman is far more complex than he himself could believe or handle. At any rate, he stands accused, with substantial evidence against him, of having reacted to his distress by committing an act of violence against a person he admired. It's not an unfamiliar pattern, but that's ultimately irrelevant. The city and county of New York, plus practically every newsgathering organization I ever heard of, is straining every nerve to determine why Chapman might have shot John Lennon, delving into Chapman's past, his movements in New York, his statements to police, everything about the poor, sick schmuck. But it doesn't matter, either. As far as can be told now, the suspect had no motive worth mentioning. If he shot John Lennon, he just did it. More murders are committed for about the same reason than might be suspected. It just happens, that's all. Motive is important only in Agatha Christie books.

The weapon: the Charter Arms .38-caliber "undercover" two-inch (barrel) model is "popular among law-enforcement officers." It would seem absolutely normal for Chapman, a former security guard, to walk into a gun store and purchase such a weapon. It cost $197, including tax. Chapman's purchase was perfectly legal. He had no criminal record, and his record of mental illness was of no concern to the state of Hawaii. In fact, he still has no record of having violated any law.

It is a dismal truth that his country discusses gun control only after someone famous has been murdered with a handgun. Lennon's death was no different. For one day, last Tuesday, distinguished public men were forced to address the issue of gun control. The president-elect, visiting New York, still opposed it. The mayor of the city still favored it. ABC's Nightline found commentators on both sides. That was that.

The next night, at the Bernard Baruch housing project on Manhattan's Lower East Side, three people - Vidal Lopez, 64; his wife, Jessie, 63; and their 11-year-old granddaughter, Doreen - were shot and killed. On Thursday a suspect was taken into custody. There was no editorial comment. Earlier that day, the mayor, in defending his city against charges that random violence is uncontrolled within it, had denounced Great Britain for its intervention in Ulster.

BY WEDNESDAY morning, the vigil front of the Dakota had become an accepted part of New York life. At 9:30 a.m., the crowd of mourners consisted of 20 or so young people, two of whom were locked in a passionate clinch against one of the building's amazing ugly Gothic outcroppings. Also present were 10 extremely gentle New York policemen, 40 or so photographers, four TV mini- cam crews, six radio people, nd print reporters too numerous to count. It was, in truth, a sweet, decent tribute. People stopped by the Dakota's iron doors, looked, wept, and moved on. Various individuals, not all of them young, passed up flowers, wreaths, drawings, even a balloon, so that the entrance of the building resembled a grossly overweight Christmas tree. But one couldn't help noticing that each time a set of TV lights was strung up, there seemed to be a lot more mourners. They weren't phonies - every tear was real - there just seemed to be a lot more tears when somebody cut to remote. Tuesday night, hundreds had sat in a cold rain to pay their respects; by Wednesday morning, a spontaneous show of grief had become a television show. By Wednesday night, when the crowds at the Dakota (where, after all, many horrified neighbors were trying to live on) reached their peak, one couldn't help feeling that many of those in attendance' were celebrating the depth of their own grief.

In that grief, they frequently said things like, "The Beatles will never die." In fact, many observers were anxious to press upon a dead John Lennon an identification with the Beatles he'd spent 10 years trying to escape. Over three days in New York, one seldom heard anyone express the conventional sentiments of sorrow for the widow and children. This was not cruelty (at least one hopes not), but rather ignorance of the fact that a man named John Lennon existed outside the lives of those who love his music. Understandable, perhaps, but the music will always be there (hell, it was played throughout the vigil at West 72nd), an Lennon is gone. Maybe that's what this clinging to grief is - people's hoping that as long a they stay sorry, it won't end, the John Lennon story will still be around to be part of and to enjoy.

But it did end, and to prolong the grieving is cruelty, an unnecessary hardship for those who did share his life. Among those, specifically, is his widow. Together, John and Yoko were in one of the great loves of our time. This week in New York, it seemed that she was thought of as a sort of strange appendage to a great man's career. She is the one who will grieve on into the future, not the sincere, if dazed, kids out on 72nd Street. It'd have been nice if more people had acknowledged it.

This has been an exciting week to work for the Daily News.

-- Clay Felker, editor of the New York Daily News Tonight

A half - hour after Felker got so excited over his paper's acquisition of an exclusive photo of Lennon signing an autograph for his alleged killer, the American free press hit what one hopes is an all- time low. Two New York television stations led their nightly news broadcasts with a live report from the funeral home where Lennon's body had been transported for preparation for cremation. Seeing the cameras, a crowd of Lennon worshipers sprang up out of the pavement of the East Side. This was idolatry, living humans drawn to the inert clay of their fallen god. And it was disgusting. Funerals should comfort the living; here were two major television stations concerned only with the disposition of a corpse. But it was all in keeping with the self- important keenings of sorrow one heard throughout this city whenever one drew near the death of John Lennon.

I understand Felker's statement, because I thought it was a good story, too. But it wasn't really. It was just another all- too-easy tale of a solid, respectable citizen wasted (it seems the only appropriate term) by a poor, twisted soul whose own life has now effectively ended. His family and loved ones have descended to the status of "sources," people worthwhile only for what they know. They, too, will live with sorrow and with hatred (Herbert Adlerberg withdrew from Chapman's case because of death threats, a lovely legacy for John Lennon). The awful probability is that neither family - the victim's nor the killer's - will ever be left alone, that both will be forced to keep on playing for the benefit of all us bystanders. This is obscene.

So on Thursday, there were two vigils for the death of John Lennon. One, slowly ending, involved about 30 people in front of the Dakota. The other, across town at the dismal red- brick enclosure of Bellevue Hospital's prison ward, will last much longer. It's termed a "suicide watch"; every 15 minutes, an officer of the New York City Department of Corrections will check on Mark David Chapman to see that he does not take his own life. That vigil is likely to be the last memorial to this murder.

John Lennon, 40, 1 West 72nd Street, New York, is survived by his wife, Yoko; their son, Sean; and a son by a previous marriage, Julian.

In lieu of flowers, it is requested that contributions be made to the Spirit Foundation, 1 Battery Park Plaza, New York, NY 10004.