Bernard C. Welch, who eluded police for years while allegedly carrying out hundreds of Washington-area burglaries, once was trailed by suspicious investigators from Pennsylvania to a hideout in the Richmond suburbs, but slipped away after Virginia State Police took over the surveillance.

Virginia investigators actually followed Welch to a house in suburban Chesterfield County during the 1975 operation, but lost him after they decided not to set up a round-the-clock watch.

"We kept someone there for a couple of hours and left," said investigator W.T. Peters. "We came back the following day, and he was gone."

At the time, Virginia and Pennsylvania authorities did not know that their quarry was Welch, who, less than a year before, had escaped from Dannermora Prison in New York, where he was serving 21 years for burglary. Welch was to stay free for another five years, until his arrest last Dec. 5 in the slaying of Washington cardiologist Dr. Michael Halberstam.

Investigators' suspicions in 1975 had been fueled by what they did know -- that the man they were trailing called himself an antique dealer, but used the name of a Charlottesville factory worker named Myron Snow. They also knew he chose to sell elegant antiques such as oriental rugs and Chippendale chairs in Lancaster County, Pa., which specialized in country antiques and was 250 miles from where he lived.

Using these shreds of evidence, investigators theorized that "Snow" might be part of an interstate burglary ring. Within a few days of the abortive stakeout at a brick rambler near Richmond, officials had ample confirmation for their suspicions.

A number of burglary victims from the Richmond area were able to identify their stolen belongings in photographs of the last shipment of antiques and other valuables that Snow/Welch took to the Conestoga Auction Co. in Lancaster before he was trailed back to Virginia. Soon after, some victims made positive identification in person in Lancaster.

"We had enough evidence then to make an arrest," said one Pennsylvania investigator, who declined to be identified. "But by then he was gone."

With state and local police now converging on the case, Welch apparently left the Richmond area and moved his alleged burglary operation to metropolitan Washington. In time, authorities were able to establish Welch's true identity, but he remained undetected until the Halberstam shooting early last month.

How authorities came so close to arresting Welch in 1975 is a story of carful, dogged police work that originated in Pennsylvania, then came to grief when Virginia State Police investigators decided against a 24-hour stakeout of the house to which Welch was trailed.

"If we were more suspicious," said Sgt. Peters, "we would have put on a more thorough surveillance . . . But we did not have enough to lay it on."

Pennsylvania authorities, who were the first to get on Welch's trail, are reluctant to place any blame, as are Richmond-area police officials, who didn't know about the surveillance operation until it failed.

One Pennsylvania official, however, after saying, "You would have a hard time convincing me there was poor police work," did add: "The net wasn't tight enough."

Summing up his feelings about the case and its tragic sequel, the official said: "It was unbelievable we were that close. This will go down as one of the great frustrations of my career."

The abortive search was triggered in August 1975, by a telephone call from Walter Bomberger, co-owner of the Conestoga Auction Co., to a friend who was an investigator with the Pennsylvania Crime Commission.

The subject of the call was one of Bomberger's better customers, a polite, well-spoken man who wanted to dispose of the tasteful consignments he brought to Conestoga's monthly antique sales. He had identified himself as Myron Snow Jr., from the Richmond area in Virginia.

"We felt he was aboveboard," said Bomberger, "but we got suspicious. We would talk to him about things he had brought, but he didn't know their true value. There would be excellent porcelains, but he didn't seem to know that. His explanation was that he was an expert in coins and jewelry, and that he had acquired all these other things at estate sales."

Bomberger's friend at the crime commission -- who declined to be identified -- was intrigued. To Bomberger's suspicions, he added his own: Why was Snow bringing fine antiques -- good engravings, Boston Chippendale and oriental rugs -- to an auction center that specialized in painted furniture, pewter and other country antiques?

Was Snow perhaps part of an interstate burglary ring?

The friend relayed his suspicions to investigators in the intelligence division of the Virginia State Police, a small, then-new unit specializing in, among other things, organized crime. The Virginia investigators turned up another intriguing bit of evidence: There was indeed a Myron Snow Jr., but according to his driving-license record, he lived in Charlottesville, not Chesterfield County.

The Pennsylvania investigator proposed a plan: He would be at Conestoga posing as a worker there when Snow arrived with his next consignment. Crime Commission investigators would follow Snow as he left Lancaster, and then "pass off" the surveillance to Virginia investigators. Flying overhead would be a Virginia State Police plane. It would know where Snow was because the cars in front and back (belonging to the Pennsylvania investigators) would be clearly marked with strips of white adhesive tape on their roofs.

Fog at Richard E. Byrd Airport kept the Virginia police plane on the ground, but otherwise the surveillance went as planned. There was a brief scare when Snow/Welch was temporarily lost outside of Richmond, but a Virginia State Police helicopter in the area picked up his trail and the ground surveillance was taken over by Sgt. Peters and his team from the intelligence division of the Virginia State Police.

Peters described what happened next:

"He stopped at a Safeway in Chesterfield. He put some groceries in his car and drove over to the house, which belonged to a woman schoolteacher he was living with. He got out of the car, took the newspaper out of the box and went into the house. That was the last time I saw him."