LEBANON, Mo. (AP) -- A man serving prison time in Kansas for murder has been convicted of killing a 15-year-old Missouri girl in 1984.

Martin Dean Priest was convicted Thursday of first-degree murder in the death of Tammy Rothganger, who went missing in May 1984 while walking to school in Eldon. A friend said she got into a car with Priest and another male. Her remains were never found.

KRCG reports court records showed Priest was living with Tammy's mother when the girl disappeared.

Priest testified Wednesday that he didn't kill Tammy. His nephew, David Nicholas, testified that he saw Priest rape Tammy and then strangle her to death.

Priest was charged in January 2016 while he was serving another life sentence in Kansas.

He will be sentenced Nov. 6.