An Alabama death row inmate, Kenneth Eugene Smith, is expected to become the first person in the US (or anywhere in the world) to be executed with nitrogen gas, after losing last-minute appeals.

The US Supreme Court and a lower appeals court declined to block what Smith’s lawyers called a “cruel and unusual” punishment.

The 58-year-old Smith, who has been on death row since 1996, was convicted in 1989 of murdering Elizabeth Sennett.

Her husband Charles Sennett, a debt-ridden preacher, had orchestrated the scheme to collect insurance money but killed himself as investigators closed in.