Slayings may share killer's distinct style, or 'signature'
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"In multiple-victim cases, we always look to see if there is a signature so we can tie victims together," said King County sheriff's Sgt. John Urquhart.
Such analysis is based on this concept: Serial killers are driven by a primitive motivation to act out the same brutality again and again, leaving behind telltale psychological markers, much like a fingerprint.
"If your case is not as strong on one murder, you could testify about behavioral characteristics and how they are maintained throughout all the murders," said Robert Keppel, a former detective, criminologist and consultant to the Green River Task Force. "So, whoever did Number 1, they also did Number 2 and Number 3."
Ridgway, a 52-year-old truck painter who lives in Auburn, is charged with murdering four Green River victims: Opal Mills, 16; Cynthia Hinds, 17; Carol Ann Christensen, 21; and Marcia Chapman, 31. Police say they have DNA samples from the bodies of Mills, Hinds and Christensen that implicate Ridgway in their killings, and other evidence that ties him to Chapman's death.
But if they are to link Ridgway to any of the 45 other Green River slayings or to dozens of other unsolved killings, they may need to rely on a signature. The remains of 37 Green River victims were little more than skeletons, found in the woods or remote areas, Keppel said. Seven victims' bodies have never been found.
Circumstantial evidence may link Ridgway to some of the slayings: He has admitted knowing a couple of the victims. Girlfriends and former wives have told police he was familiar with the remote locations where some of the bodies were left. Witnesses put him near victims around the time of their disappearance.
But that evidence might not be enough on its own. That's where signature analysis — which has been allowed in courts across the country, including Washington state — comes in.
Not same as modus operandi
Experts warn that signature analysis is a dangerous tool in untrained hands. A common mistake, even for homicide detectives, is to confuse a killer's signature with his modus operandi, or mode of operation (MO). The killer's MO is the series of actions needed to find, subdue and kill a victim, then escape detection.
In the Green River case, the killer selected prostitutes because they were vulnerable targets, an example of MO, Keppel said. The killer stopped putting more than one victim's body at a single site because he learned from news reports that detectives thought that was a telltale sign, Keppel believes.
"MO is dynamic and changes as the killer finds out what works better," Keppel said.
A killer's signature, meanwhile, consists of actions that go above and beyond the MO. An example is what is known as "posing": The killer may arrange and degrade the body after death for his own gratification and fantasies. This is different from "staging," which is moving a body to mislead pursuers.
Armchair sleuths might wonder how Ridgway could be connected to such seemingly disparate crimes as the underwater burial of a nude woman to the posing of a fully clothed woman with fish, sausages and a wine bottle displayed on her body.
Does the Green River killer have a signature?
Keppel believes so, and he thinks it's found in the four slayings in which Ridgway was charged this week. Keppel said he found this unusual signature in the slayings of prostitutes or runaways that occurred both before and after the commonly accepted time span of the Green River killings, 1982 to 1984.
Evidence not revealed
But he won't say what that signature is, concerned that revealing it could affect the course of Ridgway's prosecution. Detectives and prosecutors, likewise, will not discuss possible trial evidence.
But a picture of the Green River killer's signature emerges from interviews with Green River investigators and a close reading of books by Keppel and John E. Douglas, a retired FBI behavioral scientist who wrote the first psychological profile of the Green River killer for police in 1982.
Among the likely elements of the killer's signature are getting his gratification after death, posing and concealing the victims, and inserting objects into their bodies.
Victim Christensen, a prostitute, has attracted the most attention because of the freakish posing of her body. She was found fully clothed, with two fish placed on her chest, a wine bottle on her stomach, and sausages in her hands.
Douglas wrote several years ago that this posing indicated the killer knew his victim. Last week, Ridgway told detectives he had known Christensen, but he denied having sex with her.
Keppel said posing is rarely found in murder cases, fewer than 1 percent.
Insertion of objects in a victim's body after death is even more unusual, found in fewer than one of every 1,000 Washington slayings, he said. The bodies of two victims, Chapman and Hinds, were found with small triangular stones inserted in their vaginas.
A killer's signature may intensify over time, Keppel said, as the killer learns through experience what types of violence and victim reaction turn him on. But the underlying need — to punish and degrade the victim — remains constant.
'He was no rookie'
"By the time he got to Christensen, he was no rookie," Keppel said.
Keppel and Douglas think that sadistic sexual killers cannot stop themselves. Keppel believes that although the official Green River slayings ended in the mid-1980s, the killer probably continued killing.
But Emanuel Tanay, a highly regarded forensic psychiatrist, pointed to one of his cases, Ohio serial killer Larry Ralston, the "Angel of Death." Ralston stopped killing for six years while he worked in a morgue, Tanay said.
"Because he had enough involvement with death when he worked in a morgue, he didn't kill anybody," Tanay said. "He was satisfied."
Tanay speculated that the Green River killer might have stopped because he married and developed a sadomasochistic relationship. "He was torturing that person emotionally or physically, and it gratified his need."
Ridgway has been married three times: 1970-72, 1973-81 and 1988-present.
Signatures key in earlier cases
The King County Prosecuting Attorney's Office has successfully used signature analysis to get convictions. In the 1991 trial of George Russell, convicted of murdering women he picked up in Bellevue bars, Keppel testified to this signature: Victims were posed with objects inserted into their bodies and, for shock value, were left where they would be quickly discovered.
Signature analysis is not a hard science like DNA analysis. Sometimes, the experts don't agree with each other.
Douglas wrote that three killers may have been responsible for the deaths of the 49 Green River victims. But Keppel said, "My gut feeling is there is one person involved.
"It is pretty unusual that there would be more than one person running around doing that," he said. "That is what is so great about signature analysis."