When 18-year-old Wahab Zaaki was found bleeding to death from five stab wounds on an east London estate, police were under immense pressure to find his killer. It was spring 2009 and knife crime in the capital had been branded an epidemic. Zaaki was one of four teenagers killed in separate incidents over just three days in London that March. For the last 13 years, Kai Shannon has been in prison on a life sentence after being convicted of Zaaki’s murder and the wounding of another gang member. He has always insisted he is innocent. Shannon was among a large