Convict-author Jack Henry Abbott, his voice cracking and tears welling in his eyes, said today he killed a waiter outside a Manhattan restaurant, but that it was "a tragic misunderstanding."

He said he thought the waiter was coming at him with a knife, but now believes all the waiter was doing was escorting him to a private area outside the restaurant to relieve himself.

"Through one of the most tragic misunderstandings I can imagine," Abbott said near the end of nearly 90 minutes of testimony, then he broke down, unable to continue momentarily.

"Did there come a time you put a knife in the chest of Richard Adan?" he was asked.

"Yes."

Three times Abbott rubbed his eyes, removed his glasses and fought back tears. He sat still, then hid his head in his hands and sobbed.

In an aside to the tale of the killing of Adan, an aspiring actor and playwright, Abbott took a long pause. "Adan would have made a fine actor. He had a presence. I see it now."

The trial was interrupted when Adan's father-in-law, Henry Howard, jumped to his feet and screamed vulgarities at Abbott and author Norman Mailer, who helped Abbott win a parole from prison, where he spent nearly all of his adult life. Mailer, an observer in the courtroom and a possible witness later in the trial, appeared shaken by the outburst.

Court officers hustled Howard from the courtroom. Earlier, one of Adan's uncles angrily stalked from the courtroom.

The defense asked Justice Irving Lang for a mistrial. Lang admonished the jury to disregard the outbursts. He said the family would not be allowed to return to the court on Monday, when cross examination begins, and he reserved decision until then on the mistrial motion.

Abbott, the author of a brutally graphic prison account, "In the Belly of the Beast," is accused of stabbing to death waiter Richard Adan near dawn July 18 outside the Bini-bon restaurant. Adan, according to testimony, refused to let Abbott use an employes' restroom. The Bini-bon has no restrooms for patrons.

Abbott said he now understands that his perception of the dispute with Adan inside the restaurant was wrong. He said he realized he was mistaken "laying in his jail cell" Wednesday night after an eyewitness testified about what he saw.

The witness, Wayne Larsen, a Vietnam Marine veteran, said he saw Abbott stab Adan through the heart and that Abbott "sadistically taunted" the dying victim.

"Fundamentally, he was correct," Abbott said of Larsen. "The guy was really honest.

"I know it now," Abbott said.

"I'd been to the Bini-bon. I knew they didn't have no bathrooms."

He said he got up and Adan asked, "What are you looking for?"

"I walked over to him and said, 'What's bothering you?'

"And he said, 'What's bothering me?'

"He said, 'Do you want to go outside?'

"That's all he meant -- do I want to use the restroom," Abbott said.

He said Adan brushed him aside.

"I told him, 'Let's go outside.' "

Abbott said he did not realize Adan, an aspiring actor and playwright, was acting kindly. He said he thought Adan wanted to fight because he looked "like one of those Puerto Ricans down there that starts trouble." Abbott said he thought Adan tried "to humiliate me" in front of two women Abbott was with by refusing to take their order.

It was, he said, a misunderstanding -- "one of the most tragic misunderstandings I can imagine."