The night manager of a Washington apartment building admitted yesterday that he had lied to police when he failed to disclose that he gave the keys to the apartment of Kathleen Boyden, an advertising executive of WMAL radio, to a janitor the night Boyden was murdered.

The night manager later changed his story, according to his testimony yesterday in D.C. Superior Court, and told police that only moments before Boyden arrived at her Idaho Avenue NW apartment building the night of Sept. 17, he gave her apartment keys to David I. Garris, the building janitor charged with her murder. Garris is on trial this week.

Boyden's nude and decomposing body was found in the back seat of her car parked in the Mount Pleasant section of the city on Sept. 23, several days after she had been reported missing and police had found traces of blood in her apartment.

The night she died, Boyden had watched the television program, Shogun, with some friends, then returned to the Idaho Terrace Apartments lobby at 3040 Idaho Ave. NW, according to court testimony.

"She asked me for her messages," testified Paul Inwang, a 26-year-old Catholic University biology student who worked as a night manager in Boyden's apartment building.

"She stood by the desk and read the messages," he testified. "She said goodnight . . . I said goodnight. She went to the elevators."

About five minutes earlier, Inwang testified, Garris, 33, of 1812 Vernon St. NW, a janitor in the building, had come to the reception desk.

"He asked for the keys to 103 [boyden's apartment]. I asked him why he wanted the keys," Inwang testified. "He said he forgot something in the apartment, and wanted to go get the thing he had forgotten.

"After I gave him the keys, he went toward the elevator and shortly after that Miss Boyden came to the desk."

Inwang testified that he gave Garris the keys without signing the log book as he was supposed to do. Later when policy questioned him, Inwang said he failed to disclose when it happened because he was afraid he would lose his job for forgetting to record that Garris had taken the keys.

Assistant U.S. Attorney Richard W. Goldman said in his opening statement Wednesday that a friend of Garris's will testify during the trial that Garris later gave her a bloodied shirt to be washed.

The friend also apparently will testify, according to Goldman's statement, that later that same day, Garris asked the friend 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. Boyden's body was found in the back of her 1980 Toyota in the 3400 block of 17th St. NW, according to police reports. She had been bludgeoned to death.

Garris's attorney, Christopher G. Hoge, questioned Inwang at length about why he had lied to police. The questioning appeared designed to damage Inwang's credibility before the jury.