Escalation is a hallmark of most serial killers, but Dennis Rader, known as The BTK Killer (which stood for for "bind, torture, kill"), never followed that pattern. The time between his murders would often span years when he was seemingly dormant before the next kill, leaving investigators baffled and the town of Wichita, Kansas terrified for decades.
"His pattern is very a-typical," said Scott Bonn, PhD, a criminologist who corresponded with Rader and wrote the book "Why We Love Serial Killers: The Curious Appeal of the World's Most Savage Murders."
While most serial killers, like Jeffrey Dahmer, are compelled to kill more and more frequently until they are apprehended, Rader's 10 murder victims spanned three decades, beginning in 1974 with the murder of four members of the Otero family and ending in 1991.
Shortly after the Otero murders, he killed Kathryn Bright a few months later, but then waited three years until 1977 before attacking again. He murdered both Shirley Vian and Nancy Fox that year.
Almost eight years would pass before he struck again, killing Marine Hedge in 1985. He'd murder Vicki Wegerle the following year in 1986 before waiting nearly five more years before killing his final victim, Dolores Davis, in 1991.
"Most serial killers don't have these lengthy, extensive periods between their killings," Bonn told Oxygen.com. "Most of them really, really escalate and often times, that is what leads to their undoing."
Experts who've talked with Rader since his 2005 arrest said several factors led to the unusual timeline.
Rader's life circumstances and demands as an employee, husband and father, made it difficult for Rader to devote the time necessary to extensively stalk, research and carry out the attacks, according to Katherine Ramsland, a professor of forensic psychology at DeSales University who wrote the book "Confession of a Serial Killer: The Untold Story of Dennis Rader, the BTK Killer."
"He had to do this carefully and it had to be when he had pockets of opportunity that allowed him to pretend he was doing something else like library research for a course he was taking or being out of town or going overnight in a Boy Scouts Camping trip," she told Oxygen.com. "He always had to have a cover story."
But while years may have passed between his known killings, Ramsland, who worked closely with Rader to write the book, said he was never dormant.
"He was always looking," she said, adding that Rader gave her a list of 55 "projects" or potential victims he had tracked over the years.
"They were detailed lists with names of the projects, dates, locations, circumstances, things that would have happened to people had he had the full amount of time that he needed and they were home," she said. "It's not like he was inactive during those periods of time, it's that he didn't have all the right circumstances to go forward with something."
Bonn described Rader as a power-control killer who got more pleasure out of stalking a victim, binding them up and torturing than he did from the actual kill itself.
"It was all about the process of killing and it was almost like foreplay for sex, where it would lead up to the ultimate moment where he would kill them, but that's not really what he lived for," he said. "What he lived for was the process."
He was able to get this same sense of power and control through his jobs, first at his job at a security company installing alarm systems and later as a compliance officer in Park City, Kansas.
Bonn said Rader told him he loved carrying a badge as a compliance officer and had a reputation for strictly enforcing the rules.
"He was getting the fix that he needed to scratch his itch for power and control," he said. "I think that's one of the things that allowed him to de-escalate and have long periods between his killings because it gave him an outlet."
He also had an active autoerotic fantasy life that allowed him to re-live his killings. Bonn said Rader would cut out magazine pictures of naked women and dress up dolls in trophies he had taken from his victims to re-live his killings and satisfy his sexual needs.
"He told me in no uncertain terms in our correspondence that this enabled him to delay his killings," Bonn said, adding that at one point Rader told him the public should be "grateful" he had an autoerotic fantasy life or he may have killed more people.
Ramsland said Rader's job as a compliance officer also gave him less flexibility in his schedule and that combined with normal aging, may have slowed Rader after his last kill.
"By this time he's older so he doesn't have anywhere near the urge to do this that he used to, but he still wants to do it," she said, adding that it was more difficult then to find cover stories.
Although his last known kill was in 1991, Ramsland doesn't believe Rader ever stopped and said he had identified and attempted to carry out an attack on an 11th victim in 2004; however, a construction crew was working outside the victim's home when he had planned his attack.
"What he says is he failed, but then he picked back up and that if he hadn't been arrested he would have carried out the 11th one, because all he did was postpone it," she said.
He also fantasized about converting a silo into his own personal torture chamber during his retirement, if he was ever able to find the money or ideal location, another sign that indicated torture was never far from Rader's mind, Ramsland said.
But that dark fantasy would never become a reality. His reign of terror ended on February 25, 2005 when Rader was arrested.
"He has absolutely no remorse for his killings," Bonn said. "The only thing he has remorse over is that he got sloppy and got caught."
To learn more about Rader's brutal crimes and eventual capture, watch Oxygen's “Snapped: Notorious BTK Killer" on September 2 at 6/5 Central.
[Photo: Getty Images]
Searching for the best true crime podcasts? Subscribe to Martinis & Murder and join hosts Daryn Carp and John Thrasher as they chat about creepy crimes and unsolved mysteries... while sipping on killer drinks from our murderous mixologist Matt the Bartender. Each episode will focus on a new true crime, with all the gory details, and a cocktail recipe to get you through.