Accused killer Bernard C. Welch Jr., who law enforcement officials contend has been involved in more than 200 crimes, shaved off his hair, mustache and eyebrows just before appearing at a police lineup this week. More than 20 of his alleged victims viewed the lineup, and only one selected Welch.

Surprised at Welch's new appearance at the lineup, police outfitted him with a jet black wig and an ill-fitting bandanna as the witnesses -- all victims of burglaries, rapes and other offense said to have been committed by Welch -- tried to identify him. Instead, many pointed to a policeman disguised to look like Welch had before shaving.

According to an informed source, only one witness, a woman positively identified Welch without hesitation at the lineup, pointing him out as the man allegedly involved in a rape case in Virginia.

Law enforcement officials from the District, Maryland and Virginia, who had jointly arranged the Thursday afternoon lineup at D.C. police headquarters, were surprised and angered by Welch's apparently successful ruse.

But Welch's attorney, Sol Z. Rosen, was not. "In my opinion, they blew the lineup," Rosen said yesterday.

New lineups could be ordered by a judge, but it was unclear yesterday whether that action would be taken.

Welch's ability to remove the hair from his head and face was almost as bewildering to law enforcement officials as its success.

Less than 10 days ago, the D.C. Jail superintendent personally wrote to a D.C. Superior Court judge assuring him that special precautions had been taken to prevent any escape by Welch, who is charged with murder in the Dec. 5 shooting death of physician Michale Halberstam and who escaped from prison in Adirondack, N.Y., in 1974.

Welch had been designated for "special handling" by prison guards and was thus shackled and handcuffed when taken from his cell and placed under special superivsion because of the notoriety of his case.

Welch had appeared several weeks ago at a police lineup in connection with the Halberstam case. For that lineup, he had been ordered not to change his shaggy-haired and mustachioed appearance, which Halberstam's widow, Elliott Jones, said matched the description of the man who gunned down her husband.

But there was no similar order for this lineup, only a grand jury order that he appear at the lineup.

D.C. Corrections Department spokesman Leroy Anderson said yesterday that Welch, like any other prisoner, had the right to shave as long as there was no order prohibiting him to do so.

He said Welch had been issued the standard prisoner's toiletries kit, which includes a razor. Welch shaved in his cell, apparently unsupervised at the time. "If he chose to look like Yul Brynner, that was his privilege," Anderson said.

Rosen criticized the fact that the lineup was held even though Welch had changed his appearance. He said it was "complete police negligence to provide him with a jet black wig and mustache -- as black as my telephone -- while [Welch's] hair was brown and the witnesses were more than likely to look for a suspect with brown hair."

During the lineup, which was delayed for several hours while a wig was found for Welch to wear, police also outfitted him and other stand-ins with bandannas similar to those apparently worn while some of the crimes were committed.

However, the lineup was stopped at least once when the bandanna started slipping down Welch's face.

One source said yesterday that Welch's successful attempt to change his appearance could work against him if he went to trial for any of the cases connected to the lineup. Prosecutors suggest that such an action could be viewed as incriminating.

Welch has been held at the D.C. Jail since he was charged with the slaying of Halberstam last month.

According to court records, jail Superintendent George E. Holland informed Judge James A. Belson on Dec. 29 that Welch had been recommended and approved for "special handling" designation because of the notoriety of his case, the possibility of escape and the safety of other residents and visitors to the jail.

Under the "special handling" provisions, Welch is shackled and escorted by a minimum of two correctional officers whenever he is taken from his cell. He is kept in a solitary cell and strip-searched after every meeting with his attorney. The extreme security precautions, Rosen has argued, are "cruel" and "barbaric."

Since his arrest, police have confiscated more than 3,200 items worth $4 million from Welch's home in Great Falls, Va. More than 2,000 of those items have been identified by about 300 persons as items allegedly stolen from their homes.