An 82-year-old man died while in custody at the Oregon State Penitentiary in Salem on Saturday.

Kenneth J. Thunderbird died in the prison infirmary, according to the state department of corrections. The agency has not released what he died from.

Thunderbird was sentenced to 38 years and four months in prison after being convicted October 1996 in Clackamas County Circuit Court of first-degree rape, first-degree sodomy, first-degree sexual abuse, endangering the welfare of a minor and first-degree unlawful sexual penetration. He was found guilty of sexually assaulting at least two girls in 1995 who were 9 and 11 at the time, court records show.

His earliest possible release date was in October 2034, the state corrections department said.

Thunderbird appealed his sentence and filed motions for a new trial and DNA testing. They've been denied by Clackamas County Circuit Court. Rulings he appealed were later upheld by the Oregon Court of Appeals, state court records show.

In another motion for DNA testing filed in Clackamas County Circuit Court in May, Thunderbird described himself as a "very ill inmate," who is blind, diabetic, has mental illness and previously been stricken with polio. Prosecutors filed a response August 31, saying his motion should be denied because Thunderbird had exhausted all his appeal options.

A county circuit judge denied the motion Friday. Thunderbird died in prison the next day.

Thunderbird is the seventh Oregon prison inmate publicly announced by the Oregon Department of Corrections to have died in custody this year. Two other inmates died at the Oregon State Penitentiary in January and August.

-- Everton Bailey Jr.

ebailey@oregonian.com

503-221-8343; @EvertonBailey