Tony Ray King, 30, was convicted by a jury in St Joseph after the case was moved out of Harrison County on a change of venue.
The jury found him guilty of 1st degree murder, 2nd degree arson, and child abuse. Circuit Judge Randall Jackson ordered King to serve life without parole for murder, and 15 years for each of the other two counts. Those sentences will be served consecutively.
He is also charged with murdering his cellmate Michael Anthony Bozarth last month.
Court documents allege King strangled his the 25-year-old Bozarth in the Buchanan County Jail. Bozarth, a registered sex offender, was in the jail on allegations of molestation of two children under 9-years-old. A preliminary hearing is scheduled July 23.