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Mark Prothero was known among fellow criminal-defense attorneys as genuine, unflappable and the most decent guy in the room — even when faced with the tough task of defending Green River serial killer Gary L. Ridgway.

For years, his entire focus was to keep Ridgway from being put to death, and he did.

Mr. Prothero, a former champion swimmer at the University of Washington and a well-regarded attorney for more than 30 years, died at his Kent-area home early Saturday. He had been battling lung cancer. He was 57.

“He was a wonderful friend, a wonderful father, a wonderful lawyer. It was a great tragedy to lose someone this early in life,” said attorney Todd Gruenhagen, who was on the Ridgway defense team with Mr. Prothero.

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Mr. Prothero’s friends said that the diagnosis of lung cancer several years ago came as a surprise. He wasn’t a smoker, and he was incredibly fit.

Greg Girard, a partner at the Kent firm Hanis Irvine Prothero, said that Mr. Prothero was looking healthy when Girard saw him at the office on Friday.

Mr. Prothero was first diagnosed with lung cancer a few years ago and after treatment, it went into remission. But then it returned.

Mr. Prothero was supposed to leave for Jamaica on Easter Sunday with his wife, Kelly, and their two grown children, Sean and Marley.

“His family was so important to him,” Girard said. “They kept him focused and grounded. His kids were everything to him.”

Mr. Prothero was a star swimmer at Renton High School and swam for the Huskies for four years. He swam on the U.S. national team and was ranked 13th in the world in the 400 individual medley in 1976.

Swimming remained an important part of Mr. Prothero’s life. He coached his children and countless Kentwood High School students. He acted as an announcer at national swim meets and served as the chairman of the Pacific Northwest Swimming Board of Review. He served on the Kent Parks Foundation and played a crucial role in saving the Kent Meridian Pool from closure.

“It’s about you and a stopwatch; there are very little politics involved,” Mr. Prothero said about swimming during an interview with The Seattle Times in 2007. “It’s very pure; you can learn how hard work makes you better. It’s so valuable in terms of the life lessons that it teaches and the character it builds.”

Mr. Prothero graduated from the University of San Diego School of Law in 1981 and joined the Associated Counsel for the Accused (ACA), one of Seattle’s public-defense agencies. He left ACA in 2004 and had been in private practice ever since. He also had worked as a judge pro tem throughout King County.

“He was a consummate attorney. He was genuine. He didn’t put on airs. It was very effective,” said Don Madsen, director of ACA.

Even though he was at the center of many high-profile cases, Mr. Prothero “always made sure investigators and social workers were acknowledged,” Madsen said.

Mr. Prothero was known for his sense of humor, including drawing cartoon sketches and coming up with humorous songs.

“He would write songs and run them into a well-known melody and the songs were witty and entertaining,” Gruenhagen said.

King County Prosecutor Dan Satterberg said Mr. Prothero “was an absolute gentlemen and one of the real good guys in the legal profession.”

“He was one of those defense attorneys who was a regular guy who appealed to the average juror who wanted to believe everything he said. That’s usually the prosecutor’s schtick, to be the reasonable one,” said Satterberg, who started his legal career around the same time as Mr. Prothero.

“Mark had a lot of credibility and didn’t overly try his cases. He proved everything he said he was going to prove.”

While the Green River serial-murder case made its way through the legal system, Satterberg, as chief of staff at the prosecutor’s office, sat on the opposite side of the table from Mr. Prothero.

Satterberg called the case “unchartered territory,” not only because of the massive amount of court filings, but because the proposed plea agreement included Ridgway’s cooperation in locating victims’ remains in exchange for not being put to death.

Then-Prosecutor Norm Maleng agreed he would not seek the death penalty in exchange for that cooperation, and Ridgway then pleaded guilty to 48 killings.

Mr. Prothero co-authored a book, “Defending Gary: Unraveling the Mind of the Green River Killer,” detailing the case. Until his death, Mr. Prothero remained Ridgway’s lead lawyer.

Mr. Prothero’s friends said he was strongly opposed to the death penalty and was always hopeful he could secure Ridgway a sentence of life in prison.

“Remarkably, he was able to find the positive in people” said Gruenhagen. “He found some positive aspect in every client he represented. I think that Mr. Ridgway was lucky to have Mark for a lawyer.”

Mr. Prothero is survived by his wife, Kelly, and two children.

The family has asked that, in lieu of flowers, donations be made to the
Kent Parks Foundation
and the
Washington Husky Swimming Foundation

Information from Seattle Times archives is included in this report. Jennifer Sullivan: 206-464-8294 or On Twitter @SeattleSullivan

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