KANSAS CITY, Mo. — Federal prosecutors say a man serving a life sentence for his role in a 1988 explosion that killed six Kansas City firefighters isn’t entitled to immediate release from prison.

Bryan Sheppard’s lawyer says his sentence of life in prison without parole is unconstitutional and should be corrected because the U.S. Supreme Court has ruled recently that mandatory life-without-parole sentences of juveniles were unconstitutional. Sheppard was 17 at the time of the blast.

Sheppard was one of five people convicted in the firefighters’ deaths. They’ve all maintained their innocence.

The Kansas City Star (http://j.mp/2ddITrP ) reports that in a response filed Friday, federal prosecutors say Sheppard and the other defendants signed a waiver of their right to a jury sentencing.

Information from: The Kansas City Star, http://www.kcstar.com