Mattson, a mother of seven, was 39 years old when her body was discovered on December 9, 2003, at Camano Island State Park.
Sheriff’s detectives spent six years investigating leads and interviewing acquaintances but could not make a break in the case.
Advances in DNA technology in 2009 allowed the Washington State Patrol Crime Lab to develop a DNA profile from cellular material found on a cigarette butt near the location of Mattson’s body.
The DNA matched Schlobom, who was in the national CODIS database due to his conviction in Arizona. Authorities did not know Schlobom before the DNA match.
Investigators determined that while the DNA match placed Schlobom near the crime scene, they had to prove he was the murderer and not simply a bystander.
Rules of Evidence also prevented prosecutors from using Schlobom’s prior murder conviction in a trial.
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Over the next decade, detectives attempted to learn more about Schlobom and his connections to Mattson but found few reliable leads.
In 2019, detectives interviewed Schlobom in the Arizona prison, but he refused to answer questions.
In 2021, Schlobom sent a letter offering information about Mattson’s death in exchange for demands, which prompted a “free talk” interview with Schlobom, under temporary immunity.
Banks explained this allowed them to verify that Schlobom was the killer.
During the interview, Schlobom confessed to the murder, citing a dispute over a drug deal as his motive.
“He knew things that only the killer and detectives knew,” Detective Wallace said.
The plan was for Schlobom to sign a sworn confession and then be charged in Island County.
However, the plan fell apart when officials could not agree to a deal allowing Schlobom to serve his sentence in Washington rather than being transferred back to Arizona after pleading guilty.
Washington’s prison system was not inclined to take on a prisoner with serious medical issues, especially while there was a raging pandemic.
In 2024, a family member of Schlobom’s contacted authorities, informing them of Schlobom’s advanced dementia.
Arizona prison officials confirmed that he could no longer be prosecuted due to his mental condition.
Despite the inability to prosecute Schlobom, Banks said that he is certain Schlobom murdered Mattson, and detectives were able to provide some closure to Mattson’s family.
Sheriff Felici added that the murder grew out of a personal dispute between Schlobom and Mattson and no one else was involved.
