His health problems:

He has suffered from breathing problems related to a decades-long smoking habit. His attorneys said he has required a walker, relied on a colostomy bag and needed breathing treatments four times a day.
Prison officials planned to bring him into the death chamber in a wheelchair. ....He has chronic obstructive pulmonary disorder as the result of a decadeslong two-pack-a-day smoking habit, a prisons doctor has said.

His background:

Campbell was regularly beaten, sexually abused and tortured as a child, his attorneys have argued in court filings and before the Ohio Parole Board.

An AP reporter who was present writes:

Informed the execution was being called off, the condemned man shook hands with two members of the team and wiped away tears. “This is a day I’ll never forget,” Campbell said, according to Stebbins.

Campbell had requested he be executed by firing squad. The courts rejected his request.