rmac
Can anyone explain if there are any circumstances where a professional BOI should give way in an accident investigation to police investigators.
The simple answer is every occasion. When a police investigation has been initiated (in this case because there was a death (3 deaths)) a BOI has to be suspended. Moreover, if the BOI discovers anything that could lead to a criminal investigation then the Board's president is obliged to suspend the Board and report the matter to the relevant police authorities. The key issue revolve around Police primacy and the fact that evidence taken by a BoI is not taken in accordance with the Police and Criminal Evidence Act 1984 (PACE) and, therefore, inadmissable in a court of law.
Parrallel investigations are not permitted as there is a possibility that a BoI could predjudice an ongoing police investigation. The last BoI into a fatality (not an aircraft crash) that I sat on was suspended for nearly 2 years while police investigated and the CPS decided on wether to press charges (they did not).
There is nothing suspicious about what has been reported here. The Police are mandated to investigate any sudden death (hence the closure of motorways following a fatal accident because the area is automatically a crime scene). The investigation will first ascertain if there is the potential for a criminal act; if there is not then the scene will be handed back to the military. This is the normal course of events for post crash management.