The execution of convicted murderer Kenneth Eugene Smith using nitrogen hypoxia was "textbook," Alabama's attorney general Steve Marshall said in a news conference on Friday. 

The execution was carried out on Thursday night and marked the first time nitrogen hypoxia, a process that aims to cause asphyxiation by forcing an individual to inhale pure nitrogen or lethally high concentrations of it through a gas mask, was used to execute someone. 

"What occurred last night was textbook," Marshall said. "As of last night, nitrogen hypoxia as a means of execution is no longer an untested method. It is a proven one." 

Smith had requested the method of death after surviving a botched lethal injection in 2022, but his attorneys argued that he was being used as a "test subject," and human rights activists criticized the untried new method.

Multiple legal challenges were levied against the use of nitrogen hypoxia before the execution. On Wednesday, the Supreme Court ruled that Alabama was within its constitutional rights to carry out the execution, and on Thursday the court allowed the execution to proceed as planned. 

Marshall said Friday morning that he could hardly call the execution "justice" for the family of Elizabeth Sennett, whom Smith was convicted of killing in 1989, because of how long it took for the sentence to be carried out. Smith was one of two men who received $1,000 from Sennett's husband to kill her. Sennett's husband committed suicide a week after the killing. His accomplice Parker was executed in June 2010 for his part in the killings, according to the Alabama Department of Corrections.

Marshall apologized to the couple's sons on Friday. 

"I want to tell the family, especially the victim's sons, Mike and Chuck, how genuinely sorry I am for the horrific manner in which their mother lost her life, but I also want to apologize to them for how long it took for this sentence to be carried out," Marshall said. 

Marshall said that 43 other inmates sentenced to death in Alabama have requested execution by nitrogen hypoxia. He said that he also believes other states will begin using the method. 

"Alabama has done it, and now so can you," Marshall said. "We stand ready to assist you in implementing this method in your states." 

In:
• Alabama
• Death
• Execution

Kerry Breen

Kerry Breen is a reporter and news editor at CBSNews.com. A graduate of New York University's Arthur L. Carter School of Journalism, she previously worked at NBC News' TODAY Digital. She covers current events, breaking news and issues including substance use.

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