The Mull Chinook crash is a good case study around which to discuss these points.
Firstly, “TheSmiter” ‘s question ‘b’ (does the law differ in Scotland?):
In Scotland at the time, any such fatal accident could be subject to a FAI and the Procurator Fiscal (of the time) rigorously pursued this;
However, in England it was such that a purely military flight would not be subject to such “civvy” authority investigation – and all sorts of pressure was applied to the Proc Fisc to stop his inquiry;
Eventually, that there was one civilian passenger on board removed the MOD obstacle – but one has to ponder that if not for this, for the first couple of years at least, all that the public would have had would have been the demonstrably inadequate BOI.
From the Summary in my submission to Lord Philip’s Review last year:
<< Further to the analysis aspect, an important deficiency became apparent in the processes of investigation used by the authorities for a politically sensitive crash – that was that civil authorities were overly dependent upon the RAF for information on the aircraft's systems and pertinent operational procedures such that it was apparently easy for the RAF to obfuscate where it wanted equipment and procedures to remain out of the public domain.>>
So I would further say that not only must an independent authority be involved but they must have at their disposal independent pilots and avionics/nav experts to do the analysis and advise them re pertinent questions in any inquiry.
That the RUC didn’t wade in somehow at the time astounded me.