Adam W. Davis will remain on death row for the June 1998 murder of his teenage girlfriend's mother.
On Thursday, the Florida Supreme Court upheld Davis' death sentence for the second time.
In doing so, justices rejected his claims about the inadequate performance of the two attorneys who represented Davis at trial.
Davis was 19 when he fatally stabbed Vicki Robinson in her Carrollwood home. Despite his claim that his girlfriend, 15-year-old Valessa Robinson, proposed the killing, Davis was convicted of first-degree murder, grand theft and grand theft of an automobile.
Valessa Robinson was sentenced to 20 years in prison for her role in her mother's death.
The state's highest court also affirmed the death sentence on direct appeal in 2003.