Demetrius Terrence Frazier has been executed using controversial nitrogen gas tonight for the rape and murder of Pauline Brown - he is just the fourth criminal to be executed using the method

Demetrius Terrance Frazier was the fourth person executed in the United States using nitrogen hypoxia, which involves replacing breathable air with pure nitrogen gas

A serial rapist and murderer was put to death by nitrogen gas in Alabama on Thursday, the fourth use of the controversial execution method in the southern US state.