Tennessee has put to death a 68-year-old prisoner who suffered from dementia, brain damage and kidney and heart failure. Witnesses to Tuesday’s execution say Byron Black complained he was “hurting so bad” after prison officials strapped him to a gurney and began injecting him with a lethal dose of pentobarbital. The execution proceeded despite Black’s protests that an implanted device that regulated his heartbeat could deliver painful shocks to revive him during the execution.