Nitrogen hypoxia execution of death row prisoner branded inhumane by anaesthetist

State authorities pushed on with the controversial untried method despite claims it had the potential for 'catastrophic mishaps'.
The death chamber at Holman Correctional Facility. Photo: AAP.

A US state has gone ahead with its killing of a death row prisoner using nitrogen hypoxia despite claims it was an experimental execution method that could amount to torture.

Kenneth Smith was one of two men convicted in 1989 of murdering Elizabeth Sennett, a preacher’s wife who was stabbed and beaten to death in a $1500 contract killing arranged by her husband.