As Richard Glossip awaits execution in Oklahoma for a murder he says he didn't commit, Sky's Ian Woods examines the evidence in the case and hears a former British police officer tell Glossip it was a miscarriage of justice.

Episode four: Time running out

Sky News correspondent Ian Woods has been invited to witness the execution of a man in the US state of Oklahoma. Richard Glossip is on death row for a murder he says he didn't commit.  In this series, Woods examines the case, interviews the key people involved and discusses the controversy over the use of lethal injection.