MDOC officials say 58-year-old Marion Stanley Osborne died Tuesday.
Osborne was serving a life sentence for capital murder in the death of Patrolman Mickey Gene Johnson. Osborne was convicted in 1978 in Tishomingo County.
Authorities say the 20-year-old Johnson was shot with his own weapon on Dec. 1, 1977. He had been an officer for two years.
A segment of Mississippi Highway 25 in Belmont has been designated as the Mickey Gene Johnson Memorial Highway.