The 58-year-old was sentenced to death in 1988 for a murder of a 45-year-old woman that he carried out on behalf of the woman's husband. Since then, he has been incarcerated in the state of Alabama awaiting his death sentence.
In 2022, a failed attempt was made to inject poison as doctors were unable to find his veins. The next execution, now using nitrogen gas, is scheduled to take place sometime on Thursday.
Kenneth Smith thus becomes historic as the first person to be executed using the method, which was approved in 2018 by the state of Alabama along with Mississippi and Oklahoma.
Will die after a few minutes
According to the Alabama Attorney General, Smith will lose consciousness within seconds. Then he will die from lack of oxygen after a few minutes, reports the news agency AP.
After Smith is strapped to a gurney, a mask will be placed around his face. It is connected to a respirator that will release nitrogen gas for 15 minutes, or until Smith has had no cardiac activity for five minutes.
Not accepted by veterinary associations
The hitherto untested method has been met with strong criticism from several quarters.
Including experts at the UN Human Rights Council who warned that the method could constitute torture and humiliation as well as inhumane punishment.
The UN also draws attention to the American Veterinary Association's guidelines that the method is not accepted for several mammals. The reason is that it can cause too much stress.
The lawyers: Used as guinea pigs
Smith's lawyers have waged a legal battle to stop the execution, arguing that Alabama is using the convicted murderer as a guinea pig.
They also believe that the nitrogen gas method requires further legal review before it can be used on prisoners.