The judge approved jurors' recommendation Wednesday that Byron Scherf receive the death penalty for aggravated first-degree murder.
Scherf is a convicted rapist who already was serving life in prison when he attacked officer Jayme Biendl, 34, and strangled her with an amplifier cord at the Washington State Reformatory in Monroe in January 2011.
A Snohomish County Superior Court jury took about an hour to convict him of aggravated murder last Thursday, and the same jury on Wednesday morning recommended the death penalty. The judge formally sentenced Scherf at a later hearing.
Under Washington's death penalty law, Scherf's conviction and sentence now will undergo a mandatory review before the state Supreme Court. If Scherf opts to pursue appeals in federal courts, it could be years before an execution is carried out.
"My thoughts are with the Biendl family and with those jurors who had to listen and make a difficult decision," said deputy prosecutor Ed Stemler. "I am proud of our system of justice."
Scherf, 54, showed no reaction. He was placed in handcuffs as jurors were led from the courtroom, The Daily Herald of Everett reported.
Jurors declined to speak publicly about their verdict, but each stopped on their way from the courthouse to shake hands and exchange a few private words with deputy prosecutor Paul Stern.
Scherf never testified during the trial and offered no statement in advance of his sentencing. His lawyers didn't dispute that he strangled Biendl but suggested he didn't plan to kill her.
The jury saw Scherf's video confession and heard forensic testimony about how Biendl was strangled. Scherf said he first planned to ambush and beat up Biendl over something she said to him, but he refused to say what that was.
In the confession, Scherf detailed how he waited for other inmates to leave the chapel and ambushed Biendl as she locked up her post for the night. He told detectives that Biendl fought him and tried to call for help, but he ripped the radio from her. He said he blacked out during her death.
Corrections officers found Scherf sitting in the foyer of the chapel after realizing he wasn't in his cell during a routine inmate count. Biendl was found two hours later, after a shift officer in the main control area discovered that her radio and keys were missing.
An investigation led to the firing of three corrections officers at the prison, about 25 miles northeast of Seattle.
One was fired for being outside his assigned zone near the chapel's entrance, another for falsifying a logbook entry indicating the chapel had been cleared of prisoners, and the third for failing to properly inspect and secure the chapel when the prisoner accused in the killing was located.
Others were demoted and disciplined.
Snohomish County's medical examiner told the jury it would have taken four to five minutes of constant pressure to strangle Biendl.
Scherf's DNA was found on Biendl's fingernails. His blood was found on her coat and the amplifier cord.
In the sentencing phase of the trial, defense lawyer Karen Halverson asked jurors to spare Scherf's life, urging them not to be swayed "by the voices of vengeance or retribution."
But Stern reminded jurors of something Scherf told detectives in his confession, "If you take a life, you give a life."