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Serial killers really do live among us.

The latest example may be Dennis Rader (search), the accused "BTK Killer," who allegedly tortured and killed strangers in the Wichita, Kan., area from 1974 to 1991. He was charged this week with 10 counts of first-degree murder.

If Rader is, in fact, the killer who eluded police for more than 30 years, then he has been in plain sight all along for a quarter of a century — living in nearby Park City, Kan., a town of just under 7,000 people, mingling with neighbors and serving as a leader in his church while he was murdering his victims.

"I think we realized all along, at least in our judgment back in the 1970s and 1980s, that this person was part of our community and he was able to function among us," said Richard Lamunyan, former police chief in Wichita.

"That was one of the difficulties we were having in actually bringing him to light so we could figure out who he was. He would be, obviously, someone's neighbor. He would be shopping at the grocery stores just like everyone else. He would belong to clubs. He would have a job."

But the alleged BTK killer (search) — the self-given nickname stands for "Bind, Torture, Kill" — isn't all that different than other serial killers, such as Gary Leon Ridgway (search), the Green River Killer, who killed for years unbeknownst to his fellow community members.

"One of the things we know is that [serial killers] all lead a double life — no one ever suspects these people are going to be serial killers. They're always shocked," said Dr. Helen Morrison, author of "My Life Among Serial Killers."

"The BTK person is really no different. He was able to become as much of a chameleon so the life he led externally was a role he played. They all played this role as a person who played somebody else," she said.

And Thomas Guillen, co-author of "The Search for the Green River Killer," added: "They try to conceal themselves … they're family men, they go to church, they're Cub Scouts. They use that very well and you don't know who they are."

"In the Green River case, it was the same thing. The individual sold Amway sometimes, went to church, and they kept it very low-key so you could not detect what they're thinking, basically."

The Definition of 'Normal'

Ridgway, a truck painter for 30 years, confessed in 2003 to killing 48 women, mostly prostitutes, in the Seattle area beginning in 1982. Neighbors remembered him as a guy who had a wife, dog and cats and who loved to work in his yard and chop wood.

Another example is John Wayne Gacy (search), who, from 1978 to 1981, tortured, raped and murdered more than 30 young men in the Chicago area, then buried their bodies under the floorboards of his home and in a local river.

Gacy was a respected member of the Junior Chamber of Commerce in Des Plaines, Ill. He often dressed up as a clown to perform in children's hospitals and threw neighborhood parties. He also was a precinct captain in the local Democratic Party and the owner of his own contracting business.

"Doubling" is a term psychologists and criminal profilers use for killers and other criminals who can take part in such vicious activities while carrying on a normal life. It allows them to fly under the radar as a "normal" person while police are looking for an unidentified killer.

George Martin, former chairman of the Cub Scout troop in which Rader was involved, told FOX News that he trusted Rader with his kids and that the BTK suspect appeared to have morals and a conscience.

"In his work with the Scouts, he was a counselor for camping and hiking and biking, and he would work with the boys in that capacity, and he was very good in that capacity," Martin said.

"He was always very gentlemanly, good with the dogs (during his job as a compliance officer). The Dennis that I knew was just a quiet and gentle man … he was a fella I just looked on kind of like a brother — there was nothing unsettling at all to me."

Dr. Maurice Godwin, a criminal and geographical profiler and author of "Tracker: Hunting Down Serial Killers," said one way murderers can do this is by compartmentalizing their actions.

"I just think that he is a typical example of a complete sociopath," Godwin said. "That means that he has absolutely no empathy and has no conscience about any bad acts he's done. He's able to compartmentalize those acts and they're just completely out of his mind.

"[Ted] Bundy (search) was good at that … that's one of the reasons I think he was able to run this double life."

Bundy conducted a reign of terror across the United States between 1974 and 1978, killing young women in Washington, Utah, Colorado and Florida. He confessed to about 30 murders, but some estimate he may have killed up to 100. Before he was caught, Bundy worked with charities and even campaigned for the U.S. Republican Party.

He hid his extracurricular activities not only from coworkers and neighbors but from his wife; he also had two children.

"I think he married someone who he was able to control. He didn't have a dominant or strong-willed wife, otherwise they wouldn't have stayed married … he ruled the roost of that house," Godwin said. "When you're in a situation like that, very rarely do you have a wife who questions him … she just accepted what he did or didn't say."

Morrison, who has profiled more than 80 serial killers, observed that law enforcement on the BTK case didn't look too closely at the 59-year-old Rader, who was considered a person of interest in the 1980s and was not heavily investigated until recently, when more communiqués surfaced last year after 25 years of silence.

"He didn't look like a serial killer. They bypassed him because of whatever preconceived notion they have" of what a serial killer should be like, she said.

"What they don't understand is that these are not the people who we see who are severely mentally ill. They're not wild-eyed and disheveled and out of contact with reality. In fact, they are so capable of functioning in this role that they're the only people who really blow it."

'Evil Walks Among Us'

Rader "blew it" when he allegedly started sending messages from the BTK killer after years of lying dormant. His DNA finally got him into trouble; authorities say a blood sample from his daughter was used to confirm DNA tests that linked him to eight killings committed between 1974 and 1986.

Although most serial killers do not contact the police or media, some — like the BTK Killer and David Berkowitz (search), the "Son of Sam" killer who terrorized New York in the 1970s — taunt police and the community-at-large with notes and messages. Godwin surmised that Rader may have done this as a way to get back at the police department for not accepting him when he applied for a job there.

"Hey, he did show the police for 30 years, didn't he?" Godwin asked. "He probably thought that he was better than police."

Best-selling fiction author J.A. Jance, who was stalked by a serial killer, said the public is fascinated with serial killers and that many of them lead Jekyll-and-Hyde lives makes the real-life situation even scarier.

"I think it does make it more fascinating, because those people are a whole lot like us," Jance said. "The idea of the loner targeting people on the highway or something like that, somehow you feel a little safer about those because it's a big country. But to have someone living among you, going to church, taking out his garbage, picking up a newspaper — I think that is fascinating. It sort of goes against all the things you think are true."

She added: "I think it has to do with understanding the nature of evil and seeing that evil isn't something that exists in suicide bombers in the Middle East, that evil clearly walks among us and conceals its face."