“Robert Yates, a Spokane serial killer and a 1970 graduated from Oak Harbor High School, will plead guilty to murdering 13 women, including one woman whose body he dumped in Skagit County, as part of a plea agreement to avoid the death penalty.Spokane County Prosecutor Steve Tucker made the announcement Monday after investigators dug up a body in Yates’ Spokane yard they found with a map Yates drew in jail.Investigators believe the remains are that of Melody Murfin, a presumed victim who’s been missing for two years.Yates, a 45-year-old father of five, is expected to plead guilty to 13 counts of first-degree murder and one count of attempted murder in Spokane County Superior Court on Thursday. He will undoubtedly get a sentence of life in prison.Yet Yates may still face the death penalty in Pierce County, where prosecutors plan to charge him with two counts of aggravated first-degree murder. The charge comes with two possible penalties: life imprisonment or death.Two of the murders Yates has confessed to strike home for Whidbey Island residents. Shawn Johnson, a 1997 victim of the killing spree, lived in Spokane but her mother and a sister live in Oak Harbor.The other is 23-year-old Stacy Hawn, whose skeletal remains were found in Skagit County back in 1988.Skagit County Prosecutor Tom Verge said he was stunned last June when the Spokane County Prosecutor’s Office contacted him and said Yates confessed to killing Hawn.We had no reason to believe he was involved in the case, Verge said, adding that he doesn’t know what Yates was doing in the area at the time.Yet Hawn’s murder followed the pattern of Yates’ killing spree. Verge said Yates picked her up in Seattle at 150th and Aurora Avenue, which is an area where prostitutes hang out, in July of 1988. He killed her with a single shot to the head, Verge said, and dumped her body in an unpopulated area south of Big Lake on Lake Cavanaugh Road. Hawn’s remains weren’t found until the following December.Verge said he agreed to a change of venue in Hawn’s murder last July, which turned the case over to the Spokane County Prosecutor’s Office. In addition, Yates has admitted to killing a couple that was camping in woods near Walla Walla back in 1975.Yates has previously been linked to the murders of at least 18 women in Spokane and Tacoma, though the revelation about the Hawn murder and another murder in Walla Walla County could raise the count to 21 or more.After years of investigation into the serial killings in Western Washington – which went back at least to 1990 – a serial killer task force arrested Yates at his Spokane home April 18 on suspicion of murdering Jennifer Jones, a 16-year-old girl found dead near Mount Spokane in 1997. After the arrest, police agencies in areas where Yates once lived started looking for possible links between him and other unsolved murders. The task force has received inquiries from two foreign countries and 30 different agencies in the United States about the case against Yates.One of those was the Island County Sheriff’s Office.Sheriff Mike Hawley said he’s been in touch with Spokane investigators and has sent DNA evidence from the scene of an unsolved murder to the state crime lab for comparison to Yates. Nineteen-year-old Teresa Hesselgrave’s body was found in a wooded area near her Coupeville home April 15, 1977. She had been bound and gagged but there was no evidence of sexual assault. She died from asphyxiation.According to the Spokane Spokesman-Review, the German federal police are looking into the deaths of 26 prostitutes with assistance from U.S. Army Criminal Investigative Command.Yates, a former Navy helicopter pilot, was stationed in Goeppingen, Germany, from 1988 to 1991. The FBI has found the black van he allegedly owned in Germany and has searched it for evidence. “