Alabama completes first nitrogen gas execution

STORY: In Smith's second and final trip to the execution chamber on Thursday, executioners restrained him in a gurney and strapped a commercial industrial-safety respirator mask to his face. A canister of pure nitrogen was attached to the mask that once flowing, deprived him of oxygen.

The execution began at 7:53 p.m. (0153 GMT Friday) and Smith was declared dead at 8:25 p.m. (0225 GMT), prison officials said.

Smith appeared to remain conscious for several minutes after the nitrogen was activated, according to five journalists were allowed to watch the execution through glass as media witnesses. He then began shaking and writhing on the gurney for about two minutes, and then could be seen breathing deeply for several minutes before his breathing slowed and became imperceptible, the witnesses said.

At a press conference following the execution, Alabama Corrections Commissioner John Hamm said they believed Smith's movements on the gurney were involuntary.