(Radio Iowa) – A man convicted of killing his grandmother in her kitchen four decades ago has died in prison at the age of 64. Court records show Steve Davidson drove to the Cedar Falls Police Department in 1982 and told officers he had beaten, stabbed and choked his grandmother to death.

Davidson had argued that confession should not have been used against him due to his mental illness, but the Iowa Supreme Court upheld his life prison sentence, ruling Davidson had been calm and coherent as he told police about the murder.

State prison officials say Davidson died Sunday morning in a prison hospice unit where he had been taken due to chronic illness.