The former girlfriend of David I. Garris, the janitor in a Northwest Washington apartment building who is charged in the slaying of WMAL radio ad salesperson Kathleen Boyden, testified yesterday that Garris gave her a bloodstained shirt and other items after the murder and told her to wash the shirt.

When the woman, Renee Carter, asked Garris where he had gotten some of the items, Carter testified that Garris said that "it was none of my business." The testimony yesterday came during the second week of the Garris trial.

Boyden's nude and decomposing body was found in her 1980 Toyota parked in the 3300 block of 17th Street NW on Sept. 23, several days after she had been reported missing and police had found traces of blood in her apartment.

According to Carter's testimony, Garris asked her to drive with him to a Toyota parked on a street near Wisconsin Avenue and then follow him as he drove the Toyota to 17th Street NW, where he left it.

In testimony earlier in the trial, witnesses had said Boyden had watched television with some friends hours before her death, and then had returned to her Idaho Terrace apartment building at 3040 Idaho Ave. NW. There she picked up phone messages and walked in the direction of her apartment. Only several minutes earlier, Garris had picked up the keys to Boyden's apartment, according to testimony by the night manager of the apartment building.

Other witnesses testified that they heard screams in the apartment building the night Boyden died.

According to Carter's testimony before Judge Fred B. Ugast, Garris brought her a shirt at approximately 7 a.m. the morning of Sept. 18. "He gave me a shirt," she said. "It was white. I asked him why there was blood on the shirt. There was blood on it, around the collar. He said he got it in a fight. He asked me to wash it."

According to Carter, Garris also gave her several pieces of property, including a stereo with speakers, a tape recorder, a fur coat, jewelry, and a camera. When Carter asked Garris where the various items of property had come from, his response, she testified, was that it was "none of my business."