Florida ? A man convicted of murdering the manager of a topless bar nearly three decades ago was executed by injection Wednesday in Starke, appearing to grimace before dying 34 minutes after receiving the first of two doses of chemicals.

Angel Nieves Diaz, 55, was pronounced dead at 6:36 p.m., despite his protests of innocence and requests for clemency made by the governor of his native Puerto Rico. He appeared to move for 24 minutes after the first injection.

In most Florida executions, the prisoner loses consciousness almost immediately and stops moving within five minutes. The entire process usually takes about 15 minutes.

His final appeals to the U.S. Supreme Court challenged the chemicals used in the state’s procedure, but were rejected about an hour before his execution began.

Department of Corrections spokeswoman Gretl Plessinger said she doesn’t believe Diaz felt any pain, and his liver disease and slow metabolism prompted the second dose of lethal chemicals.