(Reuters) - An Ohio man who killed his roommate and ate part of his brain almost 40 years ago was denied parole for the sixth time, prison officials said on Thursday.

David Allen Chapin, 60, was deemed “unsuitable for release” by the Ohio Parole Board on Wednesday, said JoEllen Smith of the Ohio Department of Rehabilitation and Correction.

Chapin shot Donald Liming in the eye in their apartment in Milford, Ohio, during an argument over religion on Oct. 3, 1978. Chapin was a Baptist, while Liming had said he was a Catholic, a Buddhist and a pagan, the Cincinnati Enquirer reported.

At the time of the shooting, both men were 23 and longtime friends, the newspaper said.

During the murder trial, Chapin pleaded not guilty by reason of insanity. He told a court ordered psychiatrist that he ate Liming’s brain as part of a “mutual agreement” between the roommates, the newspaper said.

Chapin, serving a life sentence at the Allen Correctional in Lima, Ohio, cannot be considered for parole again until December 2018, Smith said.

Clermont County Prosecutor Vince Faris said his office would continue to object to the release of Chapin, supporting relatives of Liming who want Chapin to remain in prison.