The woman with whom accused murderer Bernard C. Welch has lived for five years yesterday disputed a contention by Welch's attorney that she was coerced into letting police search Welch's Great Falls home and his car after Welch's arrest in the shooting death of physician Michael Halberstam.

Appearing as a witness for the prosecution, Linda Susan Hamilton asserted that she was not aware that Welch had been charged with murder, and that she freely cooperated with police because she had nothing to hide when they asked for her permission to search the couple's Great Falls home.

Hamilton, who earlier was granted partial immunity by the U.S. Attorney's office, was called as the government's first witness to rebut efforts by Welch's attorney to bar admission of physical evidence -- including stolen property and other items -- seized at Welch's home.

D.C. Superior Court Chief Judge H. Carl Moultrie I has yet to rule on the matter, which came on the second day of pretrial hearings in the case. A jury of nine women and three men was selected in the morning session, and was sequestered at a hotel to shield it from outside influences.

Moultrie also deferred a ruling on whether Welch's legal representative should be paid with public funds pending an investigation by the U.S. Attorney's office into his financial condition. Moultrie said the government should take into account events subsequent to a previous investigation, which took place before it was disclosed that Welch had sold literary rights about his life to a New York author.

Assistant U.S. Attorney Jay B. Stephens also disclosed that the gun used to kill Halberstam had been stolen from an FBI agent. But it was Hamilton's testimony that occupied most of the afternoon in a nearly full courtroom.

Striding into the courtroom in a zebra-striped blouse and black pants, the woman, who visits Welch regularly at the D.C. Jail, asserted that she was ignorant of the alleged secret life of crime lived by the man she knew as "Norm Hamilton."

"They explained to me . . . about Bernard Welch," Hamilton said of the night Welch was arrested. "I was shook up. They started telling me about a long list of crimes he had committed, and that he was an escapee. That was the first time I heard of Bernard Welch."

She said police told her that Welch had been involved in an automobile accident when they first sought permission to search the couple's house, where they subsequently found several million dollars worth of stolen goods.

Hamilton, 32, said she granted police permission to search the house, including Welch's private basement office, because she never felt there was anything to hide.

During most of her testimony, Hamilton avoided Welch's stare, her eyes straying toward the prosecutors, the empty jury box, the spectators. Finally she ran out of places to look and once, during a short break, glanced at Welch, who noddded a solemn greeting. She paused for a moment, then her eyes darted away. Later she collapsed sobbing outside the courtroom.

Welch's attorney, Sol Z. Rosen, contended that police took advantage of Hamilton and duped her into letting them search the house and car without letting on that Welch was involved in a homicide investigation. One District detective, William Wood, admitted under questioning from Rosen that he "misrepresented the facts" to Hamilton in order to win her confidence.

The testimony was delivered out of the jury's presence as Rosen and Stephens sparred over what evidence should be admitted.