The State of Tennessee executed Nicholas Sutton, 58, by electrocution last night after Governor Bill Lee denied a clemency application supported by correction staff, victims’ family members, many of the original jurors, and those whose lives Mr. Sutton has saved.

“Nick Sutton has gone from a life-taker to a life-saver,” former federal district court judge Kevin Sharp wrote in Mr. Sutton’s clemency application. No fewer than seven former and current Tennessee correction officials supported clemency for Mr. Sutton, whom they described as “an honest, kind, and trustworthy man who has used his time in prison to better himself and show that change is possible.” One wrote that Mr. Sutton’s “efforts at self-improvement and willingness to embrace change are an inspiration.”

“Nicholas Sutton’s childhood was horrific,” a federal judge wrote in 2011. After his mother abandoned him when he was a baby, his violent, abusive, and mentally ill father beat him mercilessly. His father made his life a “living hell,” recalled Nick’s cousin, who was quoted in the clemency petition. His father beat Nick so badly he broke his arm and he held Nick and his grandmother at gunpoint, leading to an armed standoff with police. Nick became addicted to drugs after using drugs with his father at age 12, the petition explains, and his young brain suffered damage from childhood head injuries resulting in a loss of consciousness and two severe injuries to the orbital socket of the eye (he was shot in the eye as a child and hit with a lead pipe).

None of this evidence was presented to his jury, even though Nick was only 18 years old when he killed his paternal grandmother in Tennessee and two men in North Carolina. He was sentenced to life in Tennessee’s dangerous and overcrowded prisons, where incarcerated men lived in constant fear of violent attack. According to the petition, another incarcerated man attacked Nick with a lead pipe and hit him so hard that his eye became dislodged from its socket.

In 1985, Nick found himself in what former correction commissioner and warden James E. Aiken called a “kill or be killed” position with Carl Estep, an incarcerated man who told staff he planned to kill Nick. With no hope for protection from prison staff, Nick fatally stabbed Mr. Estep. He was 23 years old. Prosecutors offered him a life sentence conditioned on guilty pleas from him and his co-defendant; the petition says Mr. Sutton was willing to enter a guilty plea, but the co-defendant refused to accept a sentence to 30-40 years. Mr. Sutton was sentenced to death. (He was the only person in Tennessee under a death sentence for killing another incarcerated person.)

During his time in prison, Mr. Sutton saved the lives of three correction staff. He protected a guard from five prisoners who were trying to take him hostage during a 1985 prison riot at the Tennessee State Prison. “Nick risked his safety and well-being in order to save me from possible death. I owe my life to Nick Sutton,” the guard said in the clemency petition. “If Nick Sutton was released tomorrow, I would welcome him into my home and invite him to be my neighbor . . . It is my opinion that Nick Sutton, more than anyone else on Tennessee’s Death Row, deserves to live.”

Mr. Sutton also prevented an inmate from attacking a Sheriff’s Deputy from behind while he tried to break up a fight. And he protected a female correctional professional who had been injured in a fall. “He sprang into action, helped me to my feet, retrieved my keys and radio, and alerted staff to come to my assistance,” she said in the petition. “This was typical of Nick, who always puts others before himself and is willing to help anyone in need.”

When untreated multiple sclerosis left Paul House—who was exonerated and released from Tennessee’s death row in 2009—unable to walk, and the prison denied him a wheelchair, Mr. Sutton carried him around the prison. He took Mr. House to the shower every day, helped him wash, and carried him to visits with his mother, who told the governor in pleading for clemency, “Nick is the only reason Paul is alive today.”

Mr. Sutton also saved the life of a man who had collapsed in his cell from a punctured intestinal tract. And after Lee Hall Jr. went blind while on death row and was denied a cane or walking stick, Mr. Sutton guided him through the unit to ensure his safety. (Tennessee electrocuted Mr. Hall in December.)

Mr. Sutton studied mediation and conflict resolution to assist both peers and staff in reducing conflicts and became a leader in a combined class of divinity students and people sentenced to death taught by Dr. Graham Reside, Professor of Ethics at Vanderbilt Divinity School. In the clemency petition, Dr. Reside said that executing Nick Sutton “after such a valiant struggle to become a loving and generous witness in the world” would be unjust.

Correction officers told the governor that Mr. Sutton is “not the same man who committed those crimes.” He “has worked harder than any inmate I have known to better himself,” one said. “He has learned from his mistakes, has grown and matured, and he has become one of the most influential inmates, inspiring other inmates to better themselves.”

Five members of the jury that sentenced him to death and one alternate juror agreed that Mr. Sutton should not be executed and urged the governor to commute his death sentence. Victims’ family members—including members of the Estep, Sutton, and Almon families—also asked the governor to spare Mr. Sutton’s life.

Despite the insistence of correction staff that Mr. Sutton was “living proof of the possibility of rehabilitation and the power of redemption,” the governor denied clemency on Wednesday. Nick Sutton was the fourth person killed by the State of Tennessee since January 2019, and the seventh since the state resumed executions in August 2018.