The Island County prosecutor and sheriff officially closed a 21-year-old murder case Thursday.

Tammy Mattson, a 39-year-old Lynnwood resident and mother of seven children, was strangled to death and dumped in vegetation at Camano Island State Park on Dec. 9, 2003. The prolonged and often frustrating investigation and legal maneuvering — involving emerging DNA technology, bureaucratic red tape in two states, a chilling interrogation and unique negotiations — led officials to name 69-year-old Carl D. Schlobom as the murderer.

Schlobom won’t be answering for his crime in an Island County courtroom. He’s currently serving a life sentence in Arizona for a separate murder by strangling. Island County Prosecutor Greg Banks worked out a deal in which Schlobom would plead guilty to killing Mattson and serve the rest of his life in a Washington state prison, but it fell apart when the convicted killer suffered a series of strokes that left him with advanced dementia.

Schlobom will die in prison in Arizona without a legal record of his Island County crime, but Mattson’s family will finally have “some measure of closure,” Banks said.

A press release from the prosecutor and sheriff’s office tells a lengthy story of an investigation replete with setbacks and novel approaches to solving the crime.

For six years after the murder, detectives pursued leads and interviewed countless people in the case but kept running into dead ends, and the case eventually went cold. Investigators had collected a cigarette butt in a parking lot near where Mattson’s body was found, but DNA science was limited until years later.

Finally, in the summer of 2009, the Washington State Patrol Crime Lab was able to develop a DNA profile from cellular material left on the cigarette butt. It matched Schlobom, whose DNA had been added to the national CODIS database after he was convicted in Arizona, according to the press release. Schlobom and two others were convicted of murdering a man in a dispute over a stolen bank card, according to the Arizona Independent.

“Scientists stated that, during the rainy winter months, DNA on the cigarette butt would have degraded within a few days,” the press release states. “With the DNA match, police knew that Schlobom had been near to where Ms. Mattson’s body was found, at a time close to when she was murdered.”

But even with the DNA, investigators didn’t have enough evidence to charge Schlobom. They knew he was near the site around the time of the murder, but little else. Under court rules, the prosecution can’t disclose to a jury that Schlobom was convicted in a separate killing.

Detective Shawn Warwick, who is now a lieutenant, and Detective Ed Wallace worked the cold case but got little help from sources, the press release states. In 2019, they decided to interview Schlobom in the Arizona prison and found that he was in poor health and confined to a wheelchair. In fact, Schlobom had unsuccessfully filed lawsuits over the quality of medical care he received behind bars.

Schlobom, however, refused to answer questions.

The COVID-19 pandemic started a few months later and waylaid the investigation for well over a year. It was reinvigorated in a surprise turn. Schlobom wrote a letter to detectives in April 2021, saying he would provide information about Mattson’s murder in exchange for a long list of demands. The detectives took the letter to Banks, who has the authority to negotiated plea bargains.

“Of all his crazy demands,” Banks said, “the only one I considered was to allow him to spend the rest of his life in a Washington prison, if he turned out to be the murderer and pleaded guilty.”

Banks arranged for a “free talk” between detectives and the inmate, during which Schlobom would have a temporary grant of immunity. Banks explained that investigators were at another dead end in the case without a confession.

Before the interview, Banks, Warwick and Wallace consulted with the FBI’s Behavioral Analysis Unit on strategies for dealing with someone like Schlobom, the press release states. Afterward, they were convinced that they had the right man. Schlobom shared details that only the killer would know and filled in gaps, including the fact that he killed Mattson because of a dispute over drugs.

Schlobom was cold, matter-of-fact, and very forthcoming about the crime, the press release states.

Under the negotiated agreement, Schlobom agreed to sign a confession once the prison transfer arrangement were finalized between the Arizona and Washington Departments of Corrections. The prosecution would then charge him with premeditated murder in the first degree and kidnapping in the first degree.

Officials in both state prion systems, however, balked at the proposal, according to the press release. Washington officials were hesitant to take on a prisoner with expensive health problems. Arizona’s prison system was also unwilling to negotiate, “apparently believing that Schlobom should serve his time in an Arizona desert prison, for crimes committed in Arizona,” the releases states.

“I rattled all the cages I could,” said Banks, but he could not get the two prison agencies to agree.

A few months later, an extradition official with whom Banks remained in contact reached out and said he believed “positions had softened in both states,” the release states.

“He had relayed Banks’s persistent message that the victim’s family needed closure, and that justice should be served on Mr. Schlobom for the heinous crimes he committed in Washington, even if it added no time to his life sentence,” according to the press release.

Banks reached out to Schlobom but was met with silence. Then in October, a family member of Schlobom contacted the prosecutor and relayed that he suffered a series of debilitating strokes and had advanced dementia.

“She doubted Schlobom could read or understand the content of the letters,” the release states.

It took two months to get confirmation from Arizona prison officials, but this week officials there confirmed he is in the Special Needs Unit due to his need for round-the-clock care and monitoring. The deal was off.

In the end, Banks said he hopes Mattson’s family takes some comfort in knowing the truth about what happened and that the man responsible will spend the rest of his life in prison.

Sheriff Rick Felici said the investigation is now complete and closed.

Carl D. Schlobom