The first day of the trial focused on the violence. The following day looked at the sex. Yesterday, the jury was asked to consider whether the defendant, a Middleburg horse trainer accused of attempting to murder his wife when he found her in another man's bed, was simply insanely jealous or clinically insane.

"He said it was like a light bulb exploding. The sight of his wife on top of another man made him shoot," said Dr. Reuben Horlick, a District of Columbia psychologist testifying for the defense in the trial of the trainer, Theodore Gregory. Gregory has pleaded innocent by reason of temporary insanity to three felonies resulting from the love triange shooting last August.

Howard LaBove, 30, a Middleburg horse dealer whose bed Gregory's estranged wife was sharing, died from three gunshot wounds. Monique Gregory escaped from LaBove's cottage, running naked across a farm field to a nearby house and plunging both arms through the window of a locked door seeking refuge. Those wounds required 300 stitches.

This week Theodore Gregory is on trial not for LaBove's death, but on charges of trying to kill his own wife.

In the course of the trial, which has intrigued many and embarrassed some in Middleburg horse circles to which the Gregorys and LaBove belonged, prosecutor Thomas D. Horne has argued that Gregory was "cold-blooded" when he kicked open LaBove's bedroom door on the night of Aug. 20 and began firing a .45-caliber pistol.

"He stood at the door and said, 'I'm going to kill you, bitch,'" testified Monique Gregory on Wednesday, trembling during her two hours on the witness stand.

Yesterday attorney Blair Howard opened Gregory's defense, trying to paint a picture of a man so depressed and distraught over the loss of his wife that he was temporarily insane when he opened fire.

"It is my considered opinion that the moment Mr. Gregory [saw] Mrs. Gregory on top of Mr. LaBove in the vigorous activity of lovemaking, he was suffering from irrestible impulse," said Dr. David A. Lanham, a Washington psychiatrist called by the defense. s

Under Virginia law, a person may be innocent of an offense by reason of temporary insanity -- whether he is aware of right and wrong -- if by "mental illness or defect" the person is "deprived of the willpower to resist such an impulse."

Both Horlick and Lanham testified they considered Gregory to be suffering from a "schizoid personality disorder" during the night of the shooting. Horlick characterized that defect as one that renders a person extremely withdrawn and causes problems with interpersonal relationships. It is a person, said Horlick, "who is vulnerable to all kinds of stress functions."

Prosecutor Horne produced two psychiatrists of his own who testified that when they interviewed the defendant in jail in Leesburg, the Loudoun County seat and site of the trial, they found no evidence of mental illness.

"He was depressed but not out of keeping with his circumstances," said Dr. Stephen R. Baker, director of the county's mental health center. "My conclusion is there was no evidence of mental illness at the time of the exam. Nothing to suggest even a borderline psychosis."

But Howard argued that both of the state's psychiatrists had been interested in Gregory's condition only weeks after the shooting incident. The defense experts, said Howard, had determined Gregory's mental state on the night of the shooting.

During one particularly fractious exchange between prosecution and defense over an opinion expressed by psychologist Horlick, presiding Circuit Judge Carleton Penn sent the jury from the courtroom. After a conference with the lawyers and a consultation with his law books, Judge Penn dismissed Horlick.

"If the court were to permit this [testimony], any person who was introverted and disturbed by a personal calamity could . . . commit a crime and then have a psychologist or psychiatrist come in and say the person suffered from a mental disease," said the judge.

Judge Penn did allow Lanham to testify as to his findings and his opinions based on them. Lanham said Gregory was suffering from both a schizoid personality, which was years old, and severe clinical depression caused by the loss of his wife early last May.

Lanham described Gregory as a man whose life was going downhill.

"I think in many ways," he said, "Mr. Gregory preferred the company of horses to people."