By late August, the city was a pressure cooker, with near-record temperatures stifling residents who nonetheless locked their windows against the most notorious serial killer in years. He had murdered at least 14 people along the California coast since June 1984, seemingly at random, and all that police had to go on last Friday was a partial fingerprint from an abandoned car.

A year earlier, they might have been stuck, forced to plow through thousands of files for a likely match. But 380,000 sets of prints had been fed into the new "Cal-ID" computer system, and within three minutes, the name of Richard Ramirez kicked out in a list of 10 suspects -- a bit of electronic magic mixed with luck:

The incomplete system included only prints of offenders born since Jan. 1, 1960; Ramirez, now charged with murder and held in a Los Angeles jail, was born in February of that year.

A widely circulated artist's sketch, drawn from descriptions given by victims' who survived, bore fruit the same day. A Lompoc, Calif., woman who knew Ramirez called police and said she thought he resembled the sketch. Acquaintances told police that Ramirez had sold them jewelry, which investigators later linked to burglaries in a series of killings called the "Night Stalker" case.

At that point, police released Ramirez's name and a picture taken during a previous arrest. When Ramirez returned to Los Angeles Saturday from an apparent visit to relatives in Arizona, he was reportedly stunned to see himself on the front page of a Spanish-language paper in a liquor store, and fled into the arms of several East Los Angeles residents who collared him as he allegedly tried to steal a car in their neighborhood.

Investigators continued today to look for a gun Ramirez allegedly discarded during the chase in East Los Angeles, hoping that it will connect him to the Night Stalker murders, in which he has not been charged. He has been charged in the death May 14 of William Doi in Monterey park, and San Francisco police have issued an arrest warrant for Ramirez in connection with the Aug. 17 slaying of Peter Pan.

Police across the state said today that they are reconsidering unsolved murders and assaults for possible connections to Ramirez.

The killings attributed to the Night Stalker began in February, shortly after Ramirez was released from a six-week jail term here for car theft. But Police Chief Daryl Gates said at a news conference Wednesday that prints found in the apartment of a woman killed 15 months ago match those of Ramirez.

Ramirez received a traffic ticket five days before his arrest without being linked to the Night Stalker killings or to the sketch of the Night Stalker. In the end, two thoroughly modern tools -- the mass media and the computer -- led police to arrest their suspect in what has come to be regarded as a peculiarly modern crime.

Investigations are under way into about three dozen serial-killing cases nationwide, and many experts say they expect that number to grow if families continue to dissolve. Psychiatrists who have interviewed serial killers are focusing on a possible connection to child abuse. A recent Los Angeles Times poll found that 22 percent of a national sample of 2,627 adults said they were molested as children.

"I would say there are going to be more of these cases, what with more divorce and abandonment" said Northwestern University psychiatrist Dr. Richard Rappaport, who spent 65 hours with serial killer John Wayne Gacy in Illinois and is writing a book on serial killing. "These are some of the seeds that breed this conduct."

Satanic symbols like those left at the scene of some of the Night Stalker crimes indicate an attacker's need to strike back at parents or anyone symbolizing a family environment, said Alfred Coodley, a prominent Los Angeles psychologist who is a consultant to the county Superior Court.

"If we can define God as a father or mother concept," he said, "then this shows the child striking back for what he feels happened to him."

What has struck police here is the changing nature of the offenses they attribute to the Night Stalker -- from petty theft to child molestations to rape and murder.

"Almost without exception, serial killers are sexual sadists and psychopaths," said Dr. Park Elliott Dietz, an associate professor of law and psychiatry at the University of Virginia. Psychopaths, now often called sociopaths, are characterized by harmful conduct since childhood and may be affected in part by a genetic disorder that deadens the nervous system's ability to feel fear, he said.

Serial killers thus act boldly and often believe that they cannot be caught.

Sadists who act out their violent sexual fantasies usually find that the pleasure was not as great as they had hoped, Dietz said, and so try different victims or more violent acts in search of the expected thrill.

Dietz said most experts agree that serial killing is rising, but he cautions that there is little data to support this notion. Police simply may be more successful in linking seemingly unrelated murders because of new data-sharing programs, such as the Violent Criminal Apprehension Program at the FBI Academy in Quantico, Va.

History, he said, is full of verified serial killers whose acts dwarf the horrors of their modern counterparts. These include Vlad the Impaler, about 600 victims; Countess Bathory, about 300 victims; and Gilles de Rais, also known as Bluebeard, about 100 victims.