I note that when there's a friendly fire incident and British soldiers get killed by Americans there's an absolute ban by the US on any American military personnel attending the inquest. (Britain tells coroners US won't provide witnesses for 'friendly fire' inquests) It's come up again with the latest such incident in Afghanistan the other day.

I'm not clear if this applies to all killings - I mean would it apply to road accidents and bar-room brawls? And does it apply when it is civilians who are killed by US military in any foreign country?