The jury has heard that Jean Harris swore to make her lover's life "miserable." It has heard that Harris jumped into her car and fled the scene. Jurors have heard that Harris shot her lover four times, including once in the back. The wounds were unusual, the experts claimed, for an accidental shooting.

And today, as the prosecution wound up its case and brought on its final witness, the jury heard still more powerful evidence against Harris. The little gun she used required a strong trigger pull to go off accidentally. tTo shoot a bullet from the gun without cocking the hammer took 14 pounds of pull.

That testimony came from ballistics expert Detective Joseph Reich of the Westchester County Police.Its significance was clear: from the standpoint of a gun expert, the accidental death of Dr. Herman Tarnower may not have been an accident. But to make sure no one in the jury missed the point, Assistant District Attorney George Bolen underlined it.

"How would you define a hair trigger?" he asked the witness.

"It is extremely light trigger pull, an unsafe trigger pull, requiring about one pound," the expert said.

"And a target pull?" asked Bolen.

"Two to three pounds of pressure," the witness said.

"So with respect to trigger pull, it would be fair to suggest this weapon as neither hair trigger nor target?"

"Correct," Reich said.

He also dealt a blow to the defense position when he testified that in his opinion the gunshot wound to the victim's back -- the most serious wound of the four the doctor suffered -- was made with the muzzle of the gun 12 to 15 inches from the doctor. A weapon shot at that distance could contradict the defense position that the doctor was shot in a struggle.

Former headmistress of the Madeira School in McLean, Va., Harris, 57, has been charged with second-degree murder in the death of Tarnower in the bedroom of his Harrison, N.Y., home. The defense, speaking of the professional pressures Harris felt, of her "suicidal" tendencies and low self-esteem, maintains Harris drove to the doctor's home to kill herself. The shooting, it says, was merely a "tragic accident."

The prosecution, noting that the doctor had been seeing another woman 20 years Harris' junior, insists that Harris "intentionally, consciously" shot the doctor in a jealous rage. It also regularly notes the injuries the doctor sustained in the shooting, including the one in the back.

Today, the 2oth day of the trial, the prosecution wrapped up its case, calling as its final witness Reich, an 18-year ballistics veteran who says he has examined 15,000 weapons. In two days on the stand, Reich's testimony has been powerful. Defense attorney Joel Aurnou has insisted that Harris, the night of the shooting, tried to commit suicide, and was prevented only because her gun was broken. But Reich has testified that the gun, although somewhat damaged, with a broken cylinder hinge and bent ejector rod, was still "operational."

"I determined the gun could still function in spite of the broken parts," he told the jury.

He also testified about a bit of information that might later prove important to the case: that a bullet found imbedded in the back shelf of the doctor's headboard, was, in his opinion, the result of a "direct hit." And he said further he believed a bullet hole through a glass door of the bedroom had also been a direct hit and had not traveled through any other object. That testimony contradicts another defense contention: that Tarnower was shot in the hand while attempting to prevent Harris from shooting herself, and that the bullet that went through the doctor's hand was the same bullet that went through the glass door.

In cross-examination, defense attorney Aurnou was successful in having the detective's testimony on the glass door thrown out, on grounds it was not based on scientific evidence. He was less successful, however, in swaying the witness on the gunshot wound to Tarnower's back, even though the defense attorney pointed out that an earlier prosecution witness, the doctor who had performed the autopsy on Tarnower, had differed with the ballistics expert.

"You said the wound to the back occurred at a distance of 12 to 15 inches," said Aurnou. "Dr. Lewis Roh of the medical examiner's office made the statement that he believes the wound occurred with the muzzle of the gun at a distance of two to six inches. Would you say Dr. Roh is incorrect?"

"Yes. I disagree with Roh," the detective said.

The defense begins its case Tuesday.