Sorry to wind things up, but yes the controller would probably be at very least interview by Police very early on...possibly arrested depending on the outcome of the initial investigation. As I recall the instructions given in the met police are that in general any person concerned in the death of another would be arrested.
The decision to prosecute lays not with Police but with the Crown Procecution Service, and the chances are in the case of mutipule deaths they would put it before a jury to decide...afterall they would be critised if they didn't by public opinon.