(CN) – The use of the death penalty is racially biased and therefore violates the Washington state Constitution, a unanimous panel of the Evergreen State’s highest court ruled Thursday.

Finding that the application is applied so arbitrarily that it “fails to serve any legitimate penological goal,” the court converted the death sentences of the eight people on death row in Washington state to life in prison. That includes the death sentence of Allen Eugene Gregory, who raped, robbed and murdered 43-year-old Geneine Harshfield in 1996.

While the court agreed with Gregory’s claim on appeal that capital punishment is unfairly applied, it declined to address his conviction for aggravated first-degree murder, which it had previously affirmed.

Until now, juries in Washington state were allowed to impose the death penalty for crimes in which there was an aggravating circumstance, no mitigating factors that would merit leniency, guilt with “clear certainty,” and probability of future criminal acts. Under state law, the imposition of a death sentence was automatically reviewed by the state Supreme Court to determine whether it is excessive, based on evidence or imposed due to “passion or prejudice” and whether the defendant had an intellectual disability.

During its review of Gregory’s case, the court relied in part on a study by Katherine Beckett, a sociologist at the University of Washington, who reviewed the role of race in death penalty sentences in the state between 1981 and 2012.

Beckett found the likelihood of a jury imposing the death sentence was based substantially on the defendant’s race, with black defendants 4 ½ times more likely to be sentenced to death than white defendants who had been found guilty of similar crimes. The size of the black population in the county where the crime occurred was also a factor, Beckett found.

The state appointed a commissioner to evaluate Beckett’s research, provide the court with an overview of the disagreements between experts on the death penalty and an evaluation of the strengths and weaknesses of Beckett’s findings.

Writing for the panel, Chief Justice Mary E. Fairhurst said the process only strengthened support for Beckett’s research, and therefore Gregory’s claim that the death penalty is imposed in an arbitrary and racially biased manner.

“Given the evidence before this court and our judicial notice of implicit and overt racial bias against black defendants in this state, we are confident that the association between race and the death penalty is not attributed to random chance,” Fairhurst wrote. “Our case law and history of racial discrimination provide ample support.”

The court said it also considered the fact that capital punishment is outlawed in 19 other states, plus the District of Columbia.

“We recognize local, national, and international trends that disfavor capital punishment more broadly. When the death penalty is imposed in an arbitrary and racially biased manner, society’s standards of decency are even more offended,” Fairhurst wrote.