Alabama inmate executed with nitrogen gas was ‘shaking violently’ for 22 minutes, witnesses say

White House calls death of Kenneth Smith, executed via untested method lawyers say was cruel and unusual, very troubling'

Alabama has carried out the first execution of a death row prisoner in the US using nitrogen gas, an untested procedure which the prisoner's lawyers had argued amounted to a form of cruel and unusual punishment banned under the US constitution.

Kenneth Smith, 58, was pronounced dead at 8.25pm on Thursday evening at an Alabama prison after breathing pure nitrogen gas through a face mask to cause oxygen deprivation. The execution took about 22 minutes.