The Kent County Circuit Court jury reached the verdict Monday. Prosecutors didn't present any physical evidence against Javonte Higgins, 23, but did offer many days of circumstantial evidence.
David Bouwman, 81, and Vivian Bouwman, 80, were shot in their Kentwood home in January 2013.
Defense attorney Valerie Foster acknowledged that Higgins stole the couple's car, but said someone else must have pulled the trigger. Foster said an appeal is planned.
The Bouwmans' son-in-law, Tom Kelly, said Higgins is the "lowest form of humanity."
Higgins faces a mandatory penalty of life in prison without parole when Judge Mark Trusock Foster sentences him April 3.