The Mississippi Supreme Court has declined to hear an appeal from Zachary Conner.
He was convicted in 2005 for his role in the robbery and murder of a Vicksburg man.
The state Court of Appeals upheld Conner's conviction in May.
Prosecutors said Conner was angry after Christopher Cage won $240 in a dice game. Cage was found shot to death on a Vicksburg street in 2004.
According to the court record, two witnesses testified they saw Conner shoot Cage and run away.