The trial of the architect of the 9/11 terror attacks was halted again last month, after the US government blocked a plea deal that would have seen Khalid Sheikh Mohammed escape the death penalty; Policing Insight’s Andrew Staniforth looks back at the planning of what was described as “the most egregious criminal act on American soil in modern history”, and why the trial of the man who has admitted masterminding those events has still not come to conclusion 23 years later.