SPOKANE, Wash. — Police agencies around the state are trying to determine if confessed serial killer Robert L. Yates Jr. is responsible for more deaths.
Yates pleaded guilty Thursday to 13 murders and one attempted murder. But law enforcement officers fear the total could be higher.
"We're not convinced we have all the victims," state Atty. Gen. Christine Gregoire said.
Investigators from Washington, Oregon and British Columbia met recently to discuss the Yates case, and were puzzled by two large gaps--from 1975-88 and from 1988-96--in the murders to which Yates pleaded guilty, she said.
The 10 Spokane murders Yates pleaded guilty to occurred from 1996 to 1998, as did two Pierce County killings and an additional Spokane death for which he still faces charges. His other guilty pleas were for the murder of a young man and woman in Walla Walla County in 1975 and for killing a woman in Skagit County in 1988.
In Island County, Yates is a suspect in the 1977 slaying of 19-year-old Tracy Hesslegrave on Whidbey Island. Yates grew up in Oak Harbor, on the island just north of Puget Sound.
"He grew up in this area, knew the area, and was seen frequenting the area during this time period, and has connections to the area," Island County Sheriff Mike Hawley said Thursday.
Snohomish County detectives are investigating if Yates is connected to the 1987 deaths of a British Columbia couple, Sheriff Rick Bart said.
Tanya Van Cuylenborg, 18, was found Nov. 24, 1987, shot to death and dumped in a wooded area near Burlington in Skagit County. The body of her boyfriend, Jay Roland Cook, 20, was discovered two days later by hunters about two miles south of Monroe. He had been strangled.
The couple had been on a trip to Seattle when they were killed.
Yates has admitted dumping one of his victims' bodies in Skagit County, just months after the Cook-Van Cuylenborg murders.
Yates is also being investigated in the death of Patricia Barnes, whose body was found in Kitsap County in 1995. She had been shot.
Yates, a 48-year-old father of five, is to be sentenced next Thursday to 447 years in prison.
Spokane County investigators aren't finished with Yates either, even though he has taken responsibility for 11 murders in the county since 1996.
The special task force that caught Yates will continue to investigate the 1990 shooting deaths of Yolanda Sapp, Nickie Lowe and Kathy Brisbois and the shooting death of Sherry Palmer in 1992.
Sapp, Lowe and Brisbois were all heroin-addicted prostitutes whose bodies were left along the Spokane River. They had been shot and dumped from a car.
Yates, a former Army helicopter pilot, was stationed in Germany at the time. Detectives believe his travels could have brought him to Spokane.
The bodies of Sapp, Lowe and Brisbois did not bear Yates' signature from the 1997-98 slayings: plastic bags pulled over their heads. But the bodies of Palmer and Barnes were found with plastic grocery bags.
When Yates was arrested in April, Spokane County Sheriff Mark Sterk said he believed Yates was responsible for the four additional deaths in the county.
But during a recent polygraph test administered by defense lawyers, Yates said he didn't commit those four murders. According to those who saw the results, he passed the test.
On Thursday, Gregoire also questioned if Yates should have been offered a plea bargain to escape the death penalty.
"We believe a serial killing is a common scheme or plan that would allow us to charge aggravated first-degree murder, subject to the death penalty," Gregoire said.
Spokane County Prosecutor Steve Tucker said his survey of lawyers around the state indicated the "aggravating circumstances" needed to win a death sentence against Yates were weak.
Despite his confessions, Yates has not provided detectives with the weapons he used in the shootings.
Public defender Richard Fasy said his client would like to cooperate with law enforcement officers, but can't while he still faces a potential death penalty in the Pierce County cases.
Yates wants to remain alive for the benefit of his five children, Fasy said.
"He wants to cooperate and show remorse," Fasy said. "He wants to live, though."