An Alabama death row inmate who raped and murdered a woman in 1991 was executed this week using nitrogen gas, making him the fourth person in the U.S. to die by the controversial method.

Demetrius Terrence Frazier, 52, was executed using controversial nitrogen gas in the early hours of Friday morning - his mother begged for his life to be spared

Alabama executed Demetrius Frazier for the 1991 murder of 41-year-old Pauline Brown two days before Thanksgiving.