An autopsy found that Edna Stafford was still alive when the fire was set, according to authorities.
Henley had maintained his innocence, blaming the couple's deaths on co-defendant Terry Flatt.
Flatt testified that Henley was drunk, high on drugs and angry over a debt he believed the Staffords owed his grandparents.
Flatt served five years in prison before completing his parole last year.
Tennessee last performed its execution in September 2007.
In February 2007, the state put executions on hold when Gov. Phil Bredesen ordered a review of how Tennessee administered the death penalty.
The moratorium was lifted in May 2007 after the state's death-penalty protocols were revised. (Sources: Cnn, 04/02/2009)