The charge against LaTanya Clemmons was overturned by a state appeals court last month, but she remained in prison when prosecutors sought to have the conviction reinstated.
Her early release, after serving roughly half her sentence, was not related to her successful appeal, and a prosecutor is maintaining the effort to restore the conviction, though it would not send her back to prison.
"It's a matter of principal," said Pierce County Prosecutor Mark Lindquist on Monday.
LaTanya Clemmons was found guilty of giving criminal assistance to Darcus Allen, also known as Dorcus Allen, who police say drove the getaway car for Maurice Clemmons. Authorities say she gave Allen $50 and drove him to a motel, where he hid out.
An appeals court tossed the conviction June 22, saying there was no evidence she knew Allen was an accomplice.
Lindquist said Monday that the appeals court has it wrong: "The jury thought she knew. The jury got it right."
The prosecutorial appeal is pending before the state Supreme Court.
LaTanya Clemmons was granted early release for good behavior behind bars. She also qualified for a sentence reduction for first-time, nonviolent offenders, and she was given credit for time served in jail.
Otherwise, she would have remained in prison, waiting for the appeals process to play out.
LaTanya Clemmons has maintained that she knew Allen had been with her brother, an ex-convict from Arkansas. But she says Allen had insisted to her that he didn't know anything about the police killed at the coffee shop.
Allen was later convicted of four counts of murder for his role in the killings.
LaTanya Clemmons and five other people were charged with helping Clemmons or Allen. She and four others were convicted. One was acquitted.
Maurice Clemmons had previously been held for investigation of child rape and had posted $190,000 bail six days before the shootings.
He had been convicted in Arkansas of felonies stemming from a seven-month crime spree and was ultimately sentenced to 108 years in prison. Despite a history of violence in prison he was granted clemency in 2000 by Gov. Mike Huckabee, and Clemmons moved to Washington state.
Authorities say a grudge against police led him to ambush Sgt. Mark Renninger and Officers Tina Griswold, Ronald Owens and Gregory Richards.
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