John E. Douglas, retired FBI behavioral scientist wrote the first psychological profile of the Green River killer in 1982.

Serial killers driven to act out the same type of brutality repeatedly, leave psychological markers. "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.

Elements of the signature could be gratification after death, posing or concealing the victims and inserting objects into their bodies. A killer's signature intensifies as the killer learns through experience what types of violence and reactions arouse him. The need to punish and degrade the victim is constant.

Douglas and Robert Keppel, former detective, criminologist and consultant to the Green River Task Force, believe sadistic sexual killers cannot stop themselves. Keppel believes the Green River killer continued killing. "The likelihood of stopping is real small," Keppel said. "Every serial killer we know of in history has continued until he is stopped."

"I don't think he changed the target population, but I think he changed things enough so we weren't smart enough to see it," said Bob Gebo, former task force member, now on the Homicide Information Tips Systems team. Gebo feels there were killings after 1984.

Emanuel Tanay, forensic psychiatrist, speculates the Green River killer might have stopped killing because he married and developed a sadomasochistic relationship that fulfilled his needs, at home. "He was torturing that person emotionally or physically, and it gratified his need."

Signature analysis is not a hard science like DNA analysis. Experts don't always agree.

To tie 45 unsolved killings investigators may need to rely on a signature. Keppel believes the Green River killer has an unusual signature in the slayings that occurred both before and after the time span of 1982 to 1984.

Signature Analysis as an Investigative and Prosecutorial Tool

The King County Prosecuting Attorney's Office successfully used signature analysis to get convictions. In the 1991 trial of George Russell.

Keppel said, "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. So, whoever did Number 1, they also did Number 2 and Number 3."

Keppel won't say what that signature is in the Green River case, revealing it could interfere with trial proceedings. Detectives and prosecutors will not discuss possible trial evidence.

Modus Operandi - Mode of Operation - MO

A common mistake is to confuse a signature with a modus operandi, mode of operation or (MO).

This is the series of actions required to find, subdue and kill a victim, and escape detection. "MO is dynamic and changes as the killer finds out what works better,"Keppel said.

MO includes the type of victim taken (prostitutes and hitchhikers), where they were last seen ( Sea-Tac strip), and the way the bodies were found in clusters (5 and 6 bodies found buried in close proximity of each other). Clusters are strong evidence that only one person (or perhaps 2 acting together) was responsible for the murders.

A killer's signature, consists of actions above and beyond the MO.

Posing

A killer may arrange, pose or degrade the body, after death, for their own gratification and fantasies. Posing is rare found in less than 1% of murder cases, according to Keppel. Insertion of objects in a victim's body after death is found in fewer than 1 in 1,000 slayings.

Victim Carol Ann Christensen, was found fully clothed, with two fish placed on her chest, a wine bottle on her stomach, and sausages in her hands.

Douglas wrote posing indicated the killer knew his victim. Before his arrest, Ridgway told detectives he knew Christensen, but did not have sex with her.

"By the time he got to Christensen, he was no rookie," Keppel said.

Two Green River killer victims, Chapman and Hinds, were found with small triangular stones inserted in their vaginas.

Staging

"Staging" is different than MO or signature, staging is moving a body to mislead those attempting to locate it.

The remains of 37 victims were found in remote areas. Some victims' bodies have never been found (at least 7).