Three hours after the body of Kim Ancona, a cocktail waitress, was found naked and bloodstained in a Phoenix, Arizona, bar, the police knocked on Ray Krone’s door. It was the start of a legal nightmare that landed Mr Krone in maximum security prison for 10 years, almost three of them on death row, for a murder he did not commit.

Since his release in 2002, the 50-year-old former US air force sergeant – a one-time supporter of the death penalty – has become a campaigner against capital punishment worldwide. He has been in New York to support a resolution on global abolition that could go before the 192-member United Nations General Assembly as early as this week.