(CN) - Robert Lee Yates Jr., a serial killer who admitted to murdering more than a dozen prostitutes, cannot withdraw his 13 guilty pleas even though he was given an illegal sentence, the Washington Supreme Court ruled.
Yates, a decorated former military helicopter pilot, pleaded guilty in 2000 to murdering 13 women in Spokane County and was sentenced to 408 years in prison.
His victims were all Skid Row prostitutes in Spokane whom he solicited for prostitution, then shot in the head after intercourse and buried in rural areas.
Two years later, Yates was convicted in Pierce County of two additional murders and was sentenced to death.
The Washington Supreme Court upheld
his death sentence last year, after ruling that he could not compare his sentence to that of another serial killer, who was spared the death penalty as part of a plea bargain.
"Yates appears to believe that if some capital defendant has received life without parole, sentencing a similarly situated capital defendant to death violates RCW 10.95.130(2)(b)," Justice Susan Owens said. "But this court has repeatedly rejected the notion that proportionality requires mathematical precision or that the cases 'be matched up like so many points on a graph.' Instead, proportionality review involves merely ensuring that the death penalty is 'not imposed wantonly and freakishly.'"
On a second petition to the state's high court, Yates sought to withdraw his guilty pleas.
The en banc court found Thursday, however, that an error by the sentencing court was not prejudicial.
In this case, the sentencing judge "exceeded his statutory authority in entering the judgment and sentence," the 10-page judgment states.
"He only had authority to impose a 20-year minimum sentence for counts one and two, but instead he imposed a 20-year determinate, or maximum, sentence," Owens wrote for the majority, which included six others.
Yates claimed "that he should technically have been sentenced to 408 years with a possible extension to life in prison rather than a determinate 408-year sentence," and "is correct that his judgment and sentence is facially invalid," the judge added.
The mistake did not prejudice Yates, however, because "there was no practical effect resulting from the error," Owens wrote.
"Yates agreed to a sentence of 408 years in prison, and he should have been sentenced to a minimum of 408 years with a potential extension to a life sentence," she continued. "Given the reality of the human life-span, there is no difference between those two sentences."
Justice Gordon McCloud dissented, finding it "factually incorrect to say there was no practice effect from the error," given Yates' testimony that he would not have accepted the plea agreement if the court had correctly informed him of the sentence he would receive.
A ninth judge who concurred with the majority credited McCloud's analysis but said Yates simply failed to show prejudice.