Jack Henry Abbott, the convict-author befriended by Norman Mailer, went on trial for murder here today, charged with stabbing a man "directly in the heart" not six weeks after he had been released from prison.

The author of the best-selling "In the Belly of the Beast," a violent account of prison life, Abbott had been welcomed to New York last June by Mailer -- who intervened on Abbott's behalf for his early parole from prison -- and by other influential members of the literary community. Today, those literary lights were conspicuously absent from the courtroom. And Abbott, 37, lean and looking somewhat haggard, with only his attorneys present, heard the prosecution claim that he -- after an evening of drinking and partying -- stabbed an unarmed 22-year-old man to death.

The man, according to assistant district attorney James H. Fogel, was Richard Adan, the newly married night manager of an East Village restaurant. The stabbing allegedly occurred after an argument, which the two men had taken to the street. And the victim had been attacked, according to the prosecutor, not when he was in a position to fight, but when his back was turned.

"He made a motion to turn away," said Fogel, ". . . the defendant went after him from behind, then reached around and stabbed him directly in the heart. Stabbed him with a knife which, you will hear testimony, he had been carrying all evening. Then he returned to the restaurant and said to the women he had come in with, 'Let's get out of here, I just killed a man.' "

"The victim had no weapon of his own," Fogel again alleged. "He was not even facing the defendant when he killed him."

That account of the killing was challenged by defense lawyer Ivan Fisher. He claimed that the events were "much more detailed and complex." He also insisted that Adan had had a weapon -- a hidden knife that he had snatched from behind the restaurant counter when the fight went to the street.

"Mr. Adan was wearing a leather apron, an apron that concealed his pockets, a pocket that concealed his hands and hands that concealed his weapon," Fisher said. "We plan to establish that he had a weapon -- his own weapon -- which wound up in his heart."

Abbott, who had spent all but 9 1/2 months since the age of 12 behind bars, had received early parole this summer through the intervention of Mailer and others. Mailer hired him as a researcher and introduced him to his own agent, Scott Meredith. When Abbott's book was published this July, it received front-page notices in both The New York Times and The Washington Post. Mailer, in an introduction to the book, said he felt "all the awe one knows before a phenomenon." Other members of the literary community, meeting the author, had other feelings, of foreboding and concern.

Some saw in Abbott flashes of a sharp temper. That temper was evident in courtroom proceedings earlier this week. Abbott, outside the courtroom, could be heard screaming at his attorney for 20 minutes.

Today, there were no outbursts. Expressionless, Abbott sat beside his lawyers, in the tasteful tweed jacket they had brought, and heard his attorney term the killing a "miserable tragic accident." His lawyer also made a plea that the newly acquired fame of the author should be ignored.

"Simply because of the celebrity of the defendant, don't convert an accident into murder," he said.