Most of the Washington area home owners believed by police to have been victimized by alleged superthief Bernard C. Welch had one thing in common: They had taken inadequate security precautions against an intruder.

A survey of 25 burglary victims who think they may have been visited by the accused Welch found only one whose home had a functioning burglar alarm system -- and it protected only doors, which the burglar avoided.

The other burglarized homes also lacked many rudimentary security devices endorsed by police. According to interviews with the 25 victims.

None of the houses' windows were equipped with safety locks or other hard-to-move latches.

Only one house had bars on the windows. In that case the bars were no barrier to the thief, who simply entered via a second-story window that lacked bars.

In all but three cases, silverware, jewelry and other valuables were in obvious, easily accessible places. In fact, most of the silver stolen had been left on prominent display in dining-room hutches and buffet cabinets.

In all cases no one was at home at the time of the burglary.

None of the 25 houses was protected by a watchdog. More often than not, dogs left to "guard" a house were toy poodles or, as one rueful victim put it, "a lonely, friendly cairn terrier who was no obstacle at all."

Since they were burgled, some victims have installed, or plan to install, a wide range of protection, including electronic alarm systems, window bars, and more elaborate door and window locks. But one Montgomery County resident who lost $15,000 in silver and other valuables spoke for many when he said, "I'm not going to build a fortress. I don't want to live that way." h

Which, area police say, may have suited suspect Welch fine.

Despite his reputation as a master burglar, police say Welch may have been more industrious than imaginative. "There was nothing fantastic about his methods," said Montgomery Det. James King. He was no Pink Panther."

According to King, houses with burglar alarm systems were avoided, and the accused's most elaborate tool may have been a screwdriver.

In Henrico County, a suburban area outside Richmond where Welch also is wanted in connection with crimes, Det. Buddy Baker agreed there was nothing extraordinary about the alleged superthief's style: "He normally went through back doors, windows . . . he liked french doors. They're easier to get into . . . There was nothing fancy."

Baker offered a clue to why Welch, who is accused of fatally shooting Washington physician Michael Halberstam on Dec. 5, allegedly was able to burgle so many houses -- apparently hundreds -- without being apprehended (until Halberstam ran him down as the dying doctor tried to get to the hospital):

"He always operated alone. He never associated with known criminal types. Most people get caught bragging to somebody else or from their contacts through other criminals. He just never associated with them."

Instead of dealing with illegal fences, who might implicate him, Baker said Welch allegedly shipped his booty to a Pennsylvania auction house, which would sell it and then mail a check to Welch, who, at the time of his alleged Richmond area operations, was living in a house trailer across the street from state police headquarters.

A 1979 U.S. study called "Cost of Negligence: Losses From Preventable Household Burglaries" reached findings similar to those of The Washington Post's survey of 25 victims. Said the study:

"Entering a residential building, regardless of its type, usually presents no challenge to the average no-force burglar. The culprit has no reason to use force, nor must he/she display much technical or physical prowess since the victimized householders have often provided an unobstructed entry through their negligence."

Data from the study showed that 66 percent of all burglaries occurred when the intruder entered through an unlocked door or window.

While the much-publicized Halberstam case, in which the noted cardiologist surprised Welch inside Halberstam's Battery Place house in Northwest Washington, appears to be an exception, in some important respects it was not.

No one was at home when the burglar broke in. The burglar entered through an unlocked rear door. The Halberstams had two dogs, but neither was in the house at the time of the break-in, and both were described by D.C. police as too tame and old to put up much of a ruckus if they encountered a stranger.

Most of the burglaries in The Post's survey were prosaic affairs: The intruder pried open or kicked in a vulnerable basement door or window, sprung the lock of an unbarred patio door, or simply lifted an unlocked window.

Dr. Stanley Silverberg of Potomac, who was friend of fellow cardiologist Halberstam, was one of the three victims who had an alarm system at the time of the burglary. Still, a burglar was able to break a window, go about his business undetected and make off with silver, jewels and other goods valued at $35,000.

What happened to the alarm system?

"I am embarrassed to say, I hadn't activated it," said Silverberg. He explained that the system still was being installed but he discovered later that it could have been activated on the evening the burglar came. If the system had been turned on, the alarm would have sounded when the burglar broke through a first-floor window.

Capt. Clarence Dickerson, in charge of the District of Columbia police force's special investigations branch, says security alarms and window bars are good deterrents, but Montgomery's Det. King said such protection can lead to counterproductive complacency. He said some people do not use their alarms or even deadbolt locks after they pay for them and have them installed.

Then, too, as Dickerson pointed out, extra protection, even if it is used, is not invincible. A burglar equipped with nothing more than pliers and a screwdriver can disable any deadbolt lock, he said.

"Unfortunately," he said, "there are no fail-safe devices."