Police say Stephen Rios killed Boyle County native Jesse Valencia, back in 2004.
Valencia was a student at the University of Missouri when he was murdered.
Prosecutors believe Rios and Valencia were having an affair. Witnesses testified their relationship began after Rios arrested Valencia over noise complaints at a party.
This is the second trial for Rios. His first conviction was overturned when a Missouri appeals court ruled prosecutors used hearsay evidence.
The jury recommended a life sentence.