Jack Levin, Ph.D, knows a lot about psychopaths and serial killers.

He's the director of the Brudnick Center on Violence and Conflict at Northeastern University in Boston and the author of several books on serial killers, including "Extreme Killings." He was not surprised, he said, when serial killer Dennis Rader gave a cool and dispassionate detailing of his 10 murders during a court appearance in a Wichita, Kans., earlier this week.

Rader is better known as BTK ("bind, torture, kill") -- a name he created himself.

Click on the video box in the top right corner of this story to watch video of the BTK killer's guilty plea and chilling courtroom confession.

"For a person with a conscience, Rader's crimes seem hideous, but from his point of view, these are his greatest accomplishments and he is anxious to share all of the wonderful things he has done," Levin tells WebMD. "He held this close to his vest for three decades."

Rader's crime spree began in the 1970s and he was finally apprehended in early 2005.

During his court appearance, Rader explained how, in most of his cases, he chose, stalked, and killed his victims.

Read Web MD's "Mind of a Stalker: Why Torment Someone?"

Successful Psychopath

As many as 5 percent of people display psychopathic or sociopathic personality disorders. That's according to experts and the professional bible of mental illnesses-- the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). These personality disorders are marked by antisocial and impulsive behavior, disregard for societal standards, and no indications of fear or guilt.

In addition to being a serial killer and a psychopath, Rader was active in his church and had just been elected church council president before his arrest. He held a job as a compliance supervisor in charge of animal control. He is married and has two children.

"There is a stereotypical view that serial killers are loners, antisocial, and unable to maintain any relations, but that's mythology," Levin says.

"Rader, like so many of the others, was extraordinarily ordinary," he says. "He looked beyond suspicion, he was active in the church, a Boy Scout leader and a compliance officer, and that is the secret to the success."

Like Rader, "they don't look like sociopaths or deranged killers, because if they looked like monsters, they would be apprehended almost immediately," Levin says.

"Psychopaths wear the mask of sanity," agrees Michael Welner, MD, a forensic psychiatrist and an associate professor of psychiatry at New York University School of Medicine in New York City. Welner is also an adjunct professor of law at Duquesne University School of Law in Pittsburgh.

"Nobody would have called Dennis Rader a psychopath before he got arrested," he says.

Read Web MD's "When Employees Turn Deadly at Work."

The Abuse Excuse?

Not all psychopaths morph into criminals or serial killers, experts tell WebMD.

The BTK killer "definitely fits the characteristic of a psychopath, and he just happens to be a psychopath who evolved into a serial killer," says Jacqueline Helfgott, an associate professor of criminal justice at Seattle University in Washington.

"Throughout history there have been other people like him who can maintain a family and live a double life," she says. Rader was a "very successful psychopath."

His style in the courtroom was also typical of a psychopath, she says. "Psychopaths have low autonomic arousal. They don't react and don't show a lot of affection or emotion. They don't feel when or what other people feel."

"There are millions of sociopaths, most of whom never become serial killers," Levin says. "They may lie when they sell you a used car, but killing is not their cup of tea."

Exactly how someone like Rader becomes a psychopath and a serial killer has been hotly debated for decades.

"Some people believe there is a biological predisposition or faulty [brain] wiring, and others suggest that serial killers fail to bond during early childhood," Levin explains.

Levin says that most of them have suffered as children. "They are often physically or verbally abused, abandoned, adopted under terrible circumstances or violated by a parent and grow up with profound feelings of powerlessness," he says.

"From what I have seen, most serial killers don't begin their killing spree until their late 20s, 30s or 40, and that gives us a clue," Levin says. "It's not just childhood that creates these monsters, as most people who suffer as children grow up and become upstanding citizens. But for some reason, serial killers don't age gracefully."

Read Web MD's "Explaining Pedophilia."

A Psychopath Among Us?

So how would you be able to tell if a psychopath lived next door to you or sat next to you in church? "You wouldn't," Helfgott says. "You would have to know every segment of their life and be able to tie it all together."

"The most essential characteristic is an excessive need for power and control, and we see this in most of sexually oriented serial killers," Levin says. "They enjoy the suffering of their victims. It makes them feel special and important, like big shots."

"The last thing they would want to do is distance themselves. So they typically, like Rader, use up-close-and-personal methods to kill -- whether strangulation, stabbing, or bludgeoning," he says. "The killing is a mere footnote. The text has to do with the torture of the victim, hearing her scream. Pleading and begging for mercy makes the killer feel good."

Welner adds that "people who are true psychopaths really are cold and callous and lack empathy and have a detached way of feeling emotion."

"If they exhibit emotion, it's an effort to create an impression," he says.

And that's one of the reasons that therapy is not beneficial. "They will just learn what to tell a therapist to show that they have improved," Welner says.

To be effective, rehabilitation or prevention should involve structure and limit-setting, he says.

"The best way to set limits is with people who have the power to enforce them," Welner says, suggesting an employer who holds the purse strings or a parole officer as potentials.

Defining Depravity

Under Kansas law, Rader can be sentenced to life in prison for each charge but could become eligible for parole. He cannot face the death penalty because Kansas did not reinstate the death penalty until 1994, three years after his last killing.

Welner is now working on a new tool for jurors and judges that helps to define depravity and influence sentencing in cases like the BTK killer.

The depravity scale consists of 26 items that can help distinguish crimes and reduce the arbitrary nature of sentencing through a better working definition of depravity and heinous crimes.

"In cases like BTK, based on what he said, it's clear that he intended to emotionally traumatize victims and cause gross suffering. It was clear in the way he communicated with media that he intended to terrorize the community and clear that he got a thrill," he says. "It is unusual that his case comprises so many features that we have under study in the depravity scale," Welner says.

The scale would underscore why someone like this should be considered as the worst of the worst, he says.

By Denise Mann, MS, reviewed by Brunilda Nazario, MD

SOURCES: Jack Levin, PhD, director, Brudnick Center on Violence and Conflict, Northeastern University, Boston; author, Extreme Killings. Michael Welner, MD, forensic psychiatrist; associate professor of psychiatry, New York University School of Medicine; adjunct professor of law, Duquesne University School of Law, Pittsburgh. Jacqueline Helfgott, associate professor of criminal justice, Seattle University, Washington.