It's Missouri's third execution since since switching to the drug pentobarbital in November.
The execution was temporarily delayed Tuesday night after United States Supreme Court Justice Samuel Alito gave Smulls a temporary stay of execution, however, the high court ruled Wednesday that the state could move forward with the execution. The justices gave no reason for denying the appeal.
Smulls did not have any final words, and he was pronounced dead at 10:20 P.M.
The 56-year old was convicted of killing a jewelry store owner and injuring his wife during a 1991 robbery.