Kenneth Eugene Smith, a contract killer residing on Alabama’s death row, is scheduled for execution by nitrogen hypoxia at 6 p.m. on Thursday. Known for his criminal activities and advocacy in Italy, Smith is expected to be the first person in the United States, and indeed in the world, to be executed with nitrogen gas. This comes after Smith lost his last-minute appeals.

Alabama appears to be pioneering the use of nitrogen gas in executions, after a previously botched execution attempt. This execution will mark the first time a new method has been used for such purposes in the U.S. in over 14 months. There remains a level of controversy surrounding this new method, with some experts warning of potentially distressing experiences for the convict.

Smith was found guilty in a murder-for-hire plot that led to the death of Elizabeth Dorlene Sennett in Colbert County, Alabama. Now, the state of Alabama appears resolved to carry out his death sentence with this uncharted means of execution. The world’s attention is likely to be focused on this precedent-setting event.