Jean Harris, during the week of the Scarsdale shooting, was despondent, depressed and numb, according to her former associate at the Madeira School.

The pressures of having expelled four Madeira School seniors, an extremely unpopular decision, had left her seemingly exhausted, her associates said. One particular event, the day of the shooting of Dr. Herman Tarnower, seemed to upset her especially: a critical letter she received from a student. Its contents were not revealed in court here today, but its effect on the former headmistress were.

"She was depresed and despondent," testified Karl Wolf, director of development at Madeira School, at the Harris murder trial today. ". . . It was if a veil had been put around her face and she had aged 10 years. . . . as if someone had told her frankly she had cancer. . . . It was that much of a shock. . . ."

That letter, soucres outside the courtroom have it, was not a vicious letter, reportedly just a letter from a student who had been particularly close to the headmistress, saying that she did not agree with the headmistrees' actions regarding the suspended girls.

But its effect on Harris, according to Wolf and other Madeira staffers, was powerful. She canceled a dinner and theater appointment she had with Wolf and another staffer, and attempts to lift her out of her depression failed.

"There was no way we could get through to her," Wolf said.

"There was a glazed expression on her face," testified Ruth Anderson Katz, former English Department head.

Former headmistress of the Madeira School in McLean, Va., Harris has been on trial for two months, charged with second degree murder in the shooting death of Tarnower, her lover of 14 years, in the bedroom of his Westchester County home last March.

The prosecution has called the shooting intentional, the act of a jealous woman.

The defense insists it was an acident, a suicide attempt gone awry. It notes that Harris, the day of the shooting, drove to her lover's home with a bunch of daisies. It maintains that Harris had no feeling of hatred toward her lover, but was driven to suicide by outside pressures, particularly those at the Madeira School.

Today, the defense continued to try to define those pressures, bringing in a half dozen Madeira faculty members and students. They included Dana Schmidt (Madeira '80), a senior at the time of Harris' troubles, who had attended the school meeting Harris called after suspending the four girls.

Harris at that time was openly criticized by the students, according to Schmidt, particularly since a similar incident earlier in the school year had not been dealt with as severly. Harris did not take the criticism well, it was said.

"She was obviously flustered," Schmidt said. " . . . She seemed nervous that she was losing ground, that she was losing her position as headmistress . . . losing her position as a leader. . . . She was more flustered than I had seen her before . . . but I admired her for standing up and defending herself. . . ."

The following Monday morning, according to testmony by Karl Wolf, Harris seemed fine. He met with her to discuss a trip she had made to the West Coast, and he was, he said, extremely impressed by her knowledge. But later that day, other associates found Harris depressed, and English teacher Ruth Katz said she felt that depression had to do with the letter from the student.

"She said very little. . . . There was a glazed expession on her face . . . . It seemed more than the collapsed and breathless feeling at the end of a period of responsibility," testified Katz, an older woman who retired recently.

So marked was the difference in Harris' mood in the morning, before she received the letter, and later that afternoon, when Wolf saw Harris again, that he remarked on her mood to his wife.

Katz said she tried to cheer Harris with the gift of a bouquet of daisies, but Harris was not in her office, so Katz left the bouquet in Harris' car with a comforting note. The daisies were the same Harris took with her to the bedroom of her lover.

Also taking the stand today was James Chapman, director of the forensic lab at Corning Community College. Chapman is a licensed instructor of firearms, a police officer and holder of so many forensic talents and degrees that it took defense attorney Joel Aurnou a good 15 minutes -- during which time one distinguished member of the press fell asleep -- to enumerate them all.

The purpose of the visiting expert was clear; he was to know down the work of the local Harrison police, the same unfortunates who, earlier testimony has it, allowed Harris to wash her bloodstained blouse and who, at the crime scene, used the bloodstained telephone.

Referring to this group, the defense attorney was stern.

"Is allowing 16 persons into a crime scene, including the defendant, consistent or inconsistent with accepted, police practice in New York state?" he asked.

"Inconsistent," the witness intoned.

Rather more entertaining was a presence, this morning, in an adjacent courtroom of Tiny Tim, the entertainer. His appearance was purely coincidental, having to do with divorce attorney woes, and when he learned of the presence of Harris next door, he seemed surprised.

"Nonetheless, he had some words on love which applied to both.

"More hearts are broken by romance than by anything else in the world," he said.