Michael Wayne Hall repeatedly apologized to the victim's relatives as they watched his lethal injection from behind a window at the Huntsville prison on Tuesday, exactly 13 years after the murder.
Hall and Robert Neville were convicted in the kidnapping and murder of 19-year-old Amy Robinson. Neville was executed five years ago.
Speaking just above a whisper, Hall said he knew they caused a lot of heartache. He said, "I am sorry for everything. I wish I could take it back, but I can't."
The 31-year-old was pronounced dead at 6:23 p.m.
Courts had denied his attorney's arguments that he was mentally impaired and therefore ineligible for the death penalty.