Associated Press

SEATTLE — The man convicted of killing a Seattle police officer in 2009 has been sentenced to life in prison without the possibility of parole.

A King County Superior Court jury reached a verdict Thursday after deliberating for about an hour. Christopher Monfort was convicted last month of killing Officer Timothy Brenton. The jury rejected his insanity defense and also found him guilty of attempted murder for shooting Brenton's partner, Britt Kelly.

Officer Timothy Brenton (Seattle Police Department Image)

The prosecutor has said Monfort ambushed the officers and called it a "cold-blooded assassination."

Monfort's attorney argued his life should be spared because of his mental illness, his difficult childhood and lack of a criminal record prior to the shooting.

In the penalty phase, the jury was choosing between giving Monfort life in prison or sending him to death row.

The last person to be executed in Washington state was Cal Coburn Brown, in September 2010. He was convicted of abducting and killing Holly Washa near Seattle-Tacoma International Airport on May 23, 1991.

Monfort's defense didn't dispute that he killed Brenton and tried to kill other officers. Instead, they argued he was mentally ill, suffering from a delusional disorder.

His attorneys said Monfort believed that if enough police officers were killed, the deaths would put an end to instances of police brutality.

Monfort was accused of setting fire to police vehicles and detonating pipe bombs at Seattle's Charles Street maintenance yard on Oct. 22, 2009. He rigged the makeshift explosives to go off as officers responded to the scene, according to charging documents.

Nine days later, on Halloween night, Monfort ambushed Brenton and his then-rookie partner, Kelly, as they sat in a patrol car in Seattle's Leschi neighborhood.

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