Official describes untested 'nitrogen hypoxia' execution of Kenneth Smith – video

Alabama has carried out the first execution of a death row inmate in the US using nitrogen gas, an untested procedure that has been criticised by lawyers and activists.

Kenneth Smith, 58, was pronounced dead at 8.25pm on Thursday at the Holman correctional facility in Atmore, Alabama, after breathing pure nitrogen gas through a face mask to cause oxygen deprivation.

Officials had claimed that the new method was 'perhaps the most humane method of execution ever devised', but statements given by reporters present in the death chamber suggested otherwise

• Alabama executes Kenneth Smith using untested method of nitrogen gas