Satterberg's announcement means Michael Chadd Boysen, 27, will face life in prison without the possibility of parole if he's found guilty. He's charged with two counts of first-degree aggravated murder and is scheduled to stand trial in January.
Boysen is accused of strangling and robbing Robert R. Taylor, 82, and Norma J. Taylor, 80, in Renton in March. He was arrested three days later after a standoff at a Lincoln City, Ore., motel.
Dan Donohoe, a spokesman for the prosecutor's office, said the decision was reached after an extensive review of the case and consultation with the victims' relatives.
The dead couple were found by their daughter, Boysen's mother. The elderly couple were in the closet of their guest bedroom partially dressed in their pajamas, detectives said. Both had "severely dark/bruised ligature marks around their necks," according to charging papers.
A bloody shoelace was partially wrapped around Norma Taylor's neck.
By and large, the house remained untouched and there were no signs of struggle, but detectives did find emptied envelopes that had held $5,200. Norma Taylor's family later confirmed that she liked to save and hide cash in her home. Credit cards belonging to the couple, her cellphone and their car were also gone, charging papers said.
Detective said Boysen went on a shopping spree, spending around $1,400 at Fred Meyer and Wal-Mart to buy an iPad, a laptop, music CDs, and a pre-paid cellphone.