This much is clear: Gary L. Ridgway loved to kill.
The mystery is why.
In months of interviews with detectives, which were summarized in court documents, the Auburn truck painter divulged graphic details of his 20-year, Green River murder spree but seemed unable to articulate his motivation.
He said the prostitutes he strangled were "garbage." He said he had murderous and sexual fantasies about his mother. He admitted he lacks something most people possess: caring.
But the serial killer seemed less concerned with probing his own mind than explaining the techniques he used to kill 48 young women and elude police.
"I never really thought about it," Ridgway told a forensic psychologist who asked if he worried about having mental problems.
In that lack of introspection — and many of his other characteristics — Ridgway is typical of serial killers, say experts who have studied and stalked the rare breed of criminal.
"It's like he read the book," said Dr. Jack Levin, director of the Brudnick Center on Violence at Northeastern University in Boston and author of several books on serial murder. "He's the classic, prolific serial killer."
Though much is known about the personality traits most serial killers share, experts are still at a loss to explain what drives them to kill over and over again. Research hints that brain chemistry and structure may play a central role, but environment and upbringing are undoubtedly crucial as well.
"There's a lot of speculation, but there's not a lot of hard and fast data," said Dr. Bruce Gage, a University of Washington professor and lead psychiatrist for Western State Hospital's criminal unit.
While most people are so averse to causing harm that they will swerve their cars to avoid a squirrel, a lack of empathy and the ability to de-humanize victims are part of what allows a man like Ridgway to kill repeatedly, experts agree.
"He lacks the understanding of what it would feel like to go through what he put people through," said Dr. Michael McGrath, a forensic psychiatrist and president of the Academy of Behavioral Profiling.
"They don't mean anything to me," Ridgway said of the women he killed. He forgot what they looked like. He once choked a 16-year-old girl face to face but didn't like watching her as she gasped for air and died. He told detectives he didn't want images like that in his memory, so he strangled other victims from behind.
But it's not completely accurate to say serial killers aren't aware of their victims' suffering, Levin pointed out. It's that agony that gives the killer so much pleasure.
"Something that would make you or me squirm makes them feel wonderful," he said.
Extreme self-absorption and indifference to social norms are also common hallmarks of serial killers.
Though Ridgway gave little thought to his victims, he complained about the inconvenience involved in disposing of their bodies. Two decades after one of the murders, he remembered his irritation at breaking a taillight on his truck while unloading a corpse.
Even Ridgway was initially reluctant to admit to one abhorrent act: having sex with many of his victims after they were dead. Once he started talking about it, though, he freely detailed his actions, even describing the decomposition of the corpses.
Many serial killers shun the company of others, but Ridgway married three times, had several girlfriends and a son — though it seems his feelings for them didn't run very deep.
He said he wanted to kill his second wife by burning down their house but feared he wouldn't get away with it. He was tempted to kill his third wife.
His son he used as a cover to gain the trust of prostitutes, who lowered their guard after seeing pictures of the boy or his toys scattered around his father's truck and house. Ridgway once picked up a woman with his son in the truck and told the boy to wait in the vehicle while they took a walk in the woods. Ridgway had sex with the woman, killed her, then joined the 7-year-old boy in the truck. Had his son seen the murder, Ridgway told police, he might have killed him, too.
'I had control of her'
By necessity, serial killers are secretive, and Ridgway excelled at keeping his mouth shut. He also excelled at presenting an innocuous face to the world.
"He's been able to wear his mask longer than anybody else and get away with it," said Robert Keppel, a former chief investigator for the Washington Attorney General's Office who now teaches about serial killers at Sam Houston State University in Texas.
Ridgway maintained his mask by mentally separating his life into distinct segments, experts say. He rarely missed work at the Kenworth truck plant. He went on family outings, paid his bills, took out the trash — all while planning his kills and carrying them out.
"He had definitely compartmentalized his life," said detective Randy Mullinax, one of the Green River Task Force detectives who interviewed Ridgway. "He had work. He had family. And he had killing."
Though his job was menial and his family life unsatisfying, no one disputes that Ridgway was outstanding at what he called his "career."
"It was the one real accomplishment in his life," Levin said. "I'm sure he considers himself the Heisman Trophy winner of serial killing."
Indeed, the killer told detectives he was "good in one thing, and that's killing prostitutes."
In addition to a sense of accomplishment, serial killers seek a sense of control.
Many are unable to control most aspects of their lives, such as job and family. Many have a history of childhood abuse that they were powerless to stop.
"When they are fantasizing about killing or killing someone, they have a sense of control or mastery," McGrath said.
Ridgway described the dead women as "his property" and said he got great satisfaction from driving past sites where he had dumped bodies. He had nightmares about forgetting the locations and thus losing control of the victims.
"I had control of her when I killed her," he said, "and I'd have control over her where she was still in my possession."
The feelings of control, accomplishment and pleasure that accompany each kill can become addictive to the serial killer.
Like a junkie desperate for a fix, Ridgway would tremble with frustration when a woman refused to get in his truck or go into the woods where he could strangle her: "I had to calm down so I wouldn't look like I was, you know, scared and shaking."
A role for biology?
Though it's disturbing to consider, many of the characteristics of serial killers are not completely divorced from normal standards of behavior, many experts point out.
Everybody enjoys accomplishment and needs to exert some control over his or her life. Many people get a rush out of pursuits such as hang gliding that terrify others. Most people can rein in their sense of empathy enough to ignore the homeless, or wish misery on their enemies.
Compartmentalization allows people to carry on affairs while appearing to be loving spouses. And addictions to drugs, alcohol, gambling and risky behavior — such as patronizing prostitutes — are common.
"All human behavior is on a continuum," McGrath said.
But what is it that pushes serial killers to the far end of that spectrum?
Traditionally, the answer has been a horrific upbringing. Most serial killers were abused as children, many hideously so.
Ridgway denies abuse in his past, but it's common for killers to lie about that. He acknowledges feeling humiliated by his mother, perhaps because he wet the bed until he was a teenager. He lusted after her and wanted to stab her.
As a child, he smothered a cat. As a teen, he stabbed a boy just to see what it felt like.
All are common signs of an abuse victim lashing out at others.
Yet most abuse victims don't become serial killers.
Newer studies suggest biology may be more important in shaping the murderous mind than previously believed.
Based on interviews with more than 150 killers, including serial killer Ted Bundy, Dr. Jonathan Pincus is convinced that it usually takes the combination of three conditions to create a killer: Child abuse, brain damage and a mild mental disorder, such as paranoid thoughts.
"I believe the behavior comes from the brain," said Pincus, author of "Base Instincts: What Makes Killers Kill" and neurology chief at the Veterans Administration Hospital in Washington, D.C.
Schizophrenics and other people with profound mental illness rarely commit murder, especially serial murder, which requires meticulous planning and an ordered mind. But even though most serial killers aren't legally insane, Pincus said his studies show nearly all have something wrong with their brains. Coupled with the simmering rage fostered by child abuse, the result is violent impulses — and a mind that lacks many of the controls of a normal brain.
Brain scans have shown that many killers have damage to their frontal lobes, part of the higher brain that keeps emotions and impulses in check. Animal studies have even found that slightly different parts of the brain seem to be involved in ordinary, impulse killings and serial murder. In the latter case, there also appear to be powerful pleasure centers in the brain that, when activated, may explain the gratification killing brings to people like Ridgway.
"So maybe what's required is not just how you're raised in your first few years, but also faulty wiring and genetics and what happens to you as an adult," Levin said. "There's a lot of questions we still can't answer."
Seattle Times staff reporter Ian Ith contributed to this report. Sandi Doughton: 206-464-2491 or firstname.lastname@example.org