SPOKANE, Wash. -

The Washington State Supreme Court has rejected Spokane serial killer Robert Yates' appeal of his death sentence for the murder of two women in Pierce County.

Yates filed a boilerplate appeal with 25 separate requests for relief of his death sentence verdict from Pierce County on issues ranging from ineffective counsel, juror bias and public trial rights.

"None of Yates' claims of error clearly merit either oral review by this court," the court wrote in its decision to reject his appeal.

As part of a plea agreement in 2000, Yates pled guilty to 13 counts of first-degree murder and a single count of attempted murder. He also admitted killing an additional three people, two in Walla Walla County and another woman in Skagit County. As a result of the plea agreement Spokane County prosecutor Steve Tucker, the death penalty was taken off the table and he was sentenced to 408 years in prison.

Two years later, Yates was convicted in Pierce County of two additional counts of first degree murder. In that case he went to trial, was convicted and subsequently sentenced to death. The court upheld his death sentence in 2007 and, a year later, Yates filed his appeal, which the court rejected Thursday.

Yates was convicted in 2002 in Pierce County for the murders of Melinda Mercer and Connie LaFontaine Ellis. Mercer was killed in 1997 while Ellis was killed a year later. Both of the women were found near Camp Murray, where Yates participated in training as a Washington Army National Guard helicopter pilot.

In the time between the Mercer and Ellis killings, Yates killed an additional six women in the Spokane area.

Yates is currently behind held on the state's death row at the Walla Walla State Penitentiary.