Pushed beyond discretion by the prosecutor in her murder trial, an angry Jean Harris snapped out a story of a fierce confrontation between herself and her younger rival for the affections of Dr. Hermam Tarnower, the man Harris is accused of killing.

It was not a story the defense would have included in this trial, nor was it a story a prudent defendant would have told with such vigor and detail. It showed that Harris, despite what her attorneys have maintained in this trial, was a jealous woman -- and that when she got jealous she got angry.

"You're going to be sorry you elicited this because you've gotton a very bad version . . .," she snapped at the assistant district attorney, George Bolen, as he brought up the subject of the fight today.

But her testimony on the incident seemed to hurt the defense more than the prosecution. It involved a July weekend in 1976 when Harris was sitting by the Tarnower pool when Lynne Tryforos arrived with her two young daughters.

"Do you recall on July 10, 1976, seeing Lynne Tryforos and her two daughters at the home of Dr. Tarnower?" he asked, invoking the Other Woman's name. ". . . do you remember Lynne Tryforos arriving . . .?"

The defendant glared at him.

"I remember Lynne Tryforos arriving with a gallon of paint saying she was going to paint the doctor's furniture," she said disdainfully. "I said, 'Does it not seem bizzare that you're here painting furniture while I'm here?'"

She paused for effect.

"She didn't know what bizzare meant," she said, "I said 'Lynne, what the hell are you doing here?' She said, 'I'm here because I'm allowed to be here.' I said, 'Not when I'm here, Lynne.'"

Harris, the former headmistress of the Madeira School in McLean, Va., has been in court since October, charged with second-degree murder in the shooting of Tarnower, her lover for 14 years, in the bedroom of his Westchester County home.

She has been on the stand for five days, insisting she "never meant to harm" Tarnower, that she simply drove to his home to say goodbye before committing suicide. The prosecution, noting that Tarnower was seeing a number of other women -- including Tryforos, his assistant -- claims that Harris shot Tarnower intentionally "in jealous rage."

That being the accusation, it would befit Harris, as it would befit any accused murderer -- to show as little "rage" as possible. But today, a day of particularly nasty accusations, Harris did not remain calm -- she counterattacked and sniped.

"It gets dirtier and dirtier, it's perfectly dreadful," she snapped at the prosecutor, and "Can this go on indefinitely? It's appalling!" and "This is absolutely rotten!"

Her strongest outburst came when Bolen suggested that in February of last year, the last time she saw the doctor before the fatal shooting last March 10, she took away with her the manuscript of the doctor's new book -- without the doctor's permission.

"Oh, that's dreadful," she said. "I can't believe who would do that and muddy up Hy's life. . . . I think this is just a travesty. . . ."

She was equally outspoken, and uncharacteristically intimate, when she denied to the prosecutor that Tarnower had tried to break off the relationship that February weekend.

"Hy made love to me that morning and that's when we had a lovely talk about our relationship," she said, shocking the courtroom.

"He didn't tell you he no longer wanted to see you, that he wanted you to stay in Washington?" asked Bolen.

"Who would have told you a thing like that?" asked Harris in a small shocked voice, "Hy wouldn't . . . it isn't true . . . it would have been a strange way to say goodbye. . . ."

But it was on the subject of Tryforos, the woman whose name comes up again and again in this case, that Harris' temper flared. She seemed unable to resist the snide gratuitous comment. (No, she didn't know Tarnower saw Tryforos socially in 1975, she told the prosecutor, although she knew the woman saw the servants socially.)

She mentioned Tarnower's relationship with Tryforos in disdainful, superior tones. ("I thought it denigrated him," she said.) And when the prosecution suggested that Tryforos had promoted angry outbursts from Harris -- that she had, at one time, damaged a pair of cufflinks Tryforos had given Tarnower -- she responded angrily.

"You make up anything!" she snapped at the prosecutor. "I didn't throw the cufflinks . . . I didn't make them crack . . . if one of them cracked, it wasn't by me, Mr. Bolen."

She denied that Tarnower had suggested three months before the shooting that she and he have a "cooling-off period"; she denied knowing that Tarnower spent a week in Jamaica with Tryforos the month before the shooting. She also repeatedly denied that she was concerned over the younger woman or the attention Tryforos paid Tarnower -- including a birthday greeting that appeared as an advertisement on the front page of The New York Times when Harris and Tarnower were on holiday together.

"You saw that ad. . . ," said Bolen. "You were not at all upset?"

"I was not upset, just appalled at how tasteless it was," said Harris."It didn't seem like anything that should happen in his life in any way -- or in mine. . . ."

"Did you mention it to Dr. Tarnower?" asked the prosecutor.

"I tried to make fun of it," said Harris, "he said, 'Jesus, I hope none of my friends sees it. . . . I didn't mention that I was one of his friends, and I saw. . . ."