Jean Harris arrived at the Harrison police station the night of the Scarsdale Diet shooting in a blouse covered with blood. But when the fastidious and modest headmistress asked if she might wash it, a police matron, apparently heedless of destroying evidence, readily agreed -- even hanging it up for her afterward.

"She asked me if she could wash her blouse. I said yes," Harrison police matron Bertha Martino testified in Westchester County court today. "She took off her fur coat, then took off her blouse, then washed her blouse with her coat on."

"She washed the whole thing?" asked District Attorney George Bolen.

"Oh, sure," the matron said.

Former headmistress of the Madeira School in McLean, Va., Harris has been charged with second-degree murder in the shooting of her lover, Dr. Herman Tarnower, in the bedroom of his $500,000 home in Harrison, N.Y. The defense has contended that the shooting was a "tragic accident"; that Harris, in a state of depression went to the doctor's home to commit suicide. The prosecution -- noting that the wealthy doctor had been seeing other women -- insists the doctor was shot deliberately, in a jealous rage.

Today's witnesses, testifying for the prosecution, painted a picture neither of a depressed woman nor of an angry woman -- though a salesman in the Virginia store where Harris purchased the murder weapon characterized her, at the time of the purchase in November 1978, as "older, frail and weak." The salesman, Jamie Forst, of Irving's Sport Shop, also testified that Harris had said she was interested in purchasing a handgun "for the purpose of self-defense" and that she was, both by his assessment and her own admission, unfamiliar with guns.

"She looked at the gun as if it were a strange object," said the young salesman. ". . . she also told me she knew nothing about handguns."

Harris originally purchased a .38-caliber Smith and Wesson, but never picked it up, Forst said. He testified that she eventually returned to purchase a smaller .32-caliber pistol.

"She felt the [larger] gun was too big for her hand that she could handle a smaller weapon more effectively."

Also testifying today was Madeira School building superintendent Lewis Andrew Baughman Jr. -- a man whose presence at first made Harris put on her dark glasses, a gesture she seems to make when most uncomfortable.

Testifying for the prosecution, Baughman said that he had filled the gas tank of Harris' car the night of the murder, that she said at the time that she was late for a dinner party and that Harris -- who had a small bouquet of daisies in the car beside her -- appeared that night to be normal.

But under cross-examination later the defense was able to evoke another sort of information from Baughman -- information that painted Harris as sensitive, tender and conscientious. Harris was seen as a woman who picked up orange peels and trash when she saw them on the grounds; a woman who, when the students made Christmas wreaths, "was there, working alongside them"; a woman who cared about even the children of the man who took care of the buildings.

"Tell me about the conversation you had with Mrs. Harris about summer camp," defense attorney Joel Aurnou asked.

Baughman smiled. "She called me in and pretended like she was mad at me and said, 'Your kids aren't in camp -- I see them lookin' at the other kids -- I want them in camp tomorrow," recalled Baughman

Aurnou smiled, pressing for more.

"Once in a while the johns overflowed and I remember she was in there mopping the floors . . . ," said Baughman. The prosecution, unable to bear any more, spoke up.

"Judge, really . . . ," said Bolen.

The objection was sustained.