Black’s US lawyers raised concerns that his heart implant could shock him back to life, leading to undue suffering.

The state of Tennessee carried out the execution of Byron Black on Tuesday morning. The 69-year-old was convicted of killing his girlfriend and her daughters in 1988. The execution was carried out despite uncertainty about Black’s heart implant.

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.