The state executed Black after Tennessee Gov. Bill Lee declined requests from attorneys, advocacy groups and even some Republicans to intervene.

Byron Black was executed after a back-and-forth in court over whether officials would need to turn off his implantable cardioverter-defibrillator, or ICD. Black, 69, was in a wheelchair, suffering from dementia, brain damage, kidney failure, congestive heart failure and other conditions, his attorneys have said.

Tennessee is set to execute death row inmate Byron Black on Tuesday despite raised concerns about his implanted heart device which could cause a "prolonged and torturous execution."