What happened at America's first nitrogen gas execution

As witnesses including five news reporters watched through a window, Kenneth Eugene Smith, who was convicted and sentenced to die in the 1988 murder-for hire slaying of Elizabeth Sennett, convulsed on a gurney as Alabama carried out the nation's first execution using nitrogen gas.

Critics who had worried the new execution method would be cruel and experimental said Smith's final moments on Thursday night proved they were right. Alabama Attorney General Steve Marshall, however, characterised it on Friday as a "textbook" execution.

Here is an eyewitness account of how it unfolded. Times, unless otherwise noted, are according to a clock on the execution chamber wall at the William C. Holman Correctional Facility.

Mask check

The curtains between the viewing room and the execution chamber opened at 7:53 pm [local time]. Smith, wearing a tan prison uniform, was already strapped to the gurney and draped in a white sheet.

A blue-rimmed respirator mask covered his face from forehead to chin. It had a clear face shield and plastic tubing that appeared to connect through an opening to the adjoining control room.

Final words

The prison warden entered the chamber, read the death warrant setting his execution date and held a microphone for Smith to speak any final words.

"Tonight Alabama causes humanity to take a step backwards," Smith began. He moved his fingers to form an "I love you" sign to family members who were also present. "I'm leaving with love, peace and light. ... Love all of you."

The Sennett family watched from a viewing room that was separate from the one where members of the media and Smith's attorney were seated.

Execution is greenlighted

Marshall, the attorney general, gave prison officials the OK to begin the execution at 7:56 pm [local time]. That was the final confirmation from his office that there were no court orders preventing it from going forward.

A corrections officer in the chamber approached Smith and checked the side of the mask.

The Rev. Jeff Hood, Smith's spiritual advisor took a few steps toward Smith, touched him on the leg and they appeared to pray.

Later Hood called the execution of the convicted murderer "torture", "cruel" and "unusual punishment."

The Department of Corrections had required Hood to sign a waiver agreeing to stay 3 feet away from Smith’s gas mask in case the hose supplying the nitrogen came loose.

Gasping breathes

Smith began to shake and writhe violently, in thrashing spasms and seizure-like movements, at about 7:58 pm. The force of his movements caused the gurney to visibly move at least once.

Smith's arms pulled against the straps holding him to the gurney. He lifted his head off the gurney and then fell back.

The shaking went on for at least two minutes. Hood repeatedly made the sign of the cross toward Smith. Smith's wife, who was watching, cried out.

Smith began to take a series of deep gasping breaths, his chest rising noticeably. His breathing was no longer visible at about 8:08 pm. The corrections officer who had checked the mask before walked over to Smith and looked at him.

Execution ends

The curtains were closed to the viewing room at about 8:15 pm.

Alabama Corrections Commissioner John Q. Hamm told reporters afterward that the nitrogen gas flowed for approximately 15 minutes.

The state attorney general's office declined on Friday to discuss at what time the nitrogen gas began flowing, or at what time a monitor connected to Smith during the execution showed that his heart had stopped beating.

State officials said Smith was pronounced dead at 8:25 pm.