I have to disagree. The AAIB investigation simply collects facts and looks for causes. The facts are unbiased and available to all. Any and all facts accumulated by the AAIB investigation should be available to the police, the CPS and the defence should it be deemed that a crime may have taken place. You can't simply say that as certain facts were established by the AAIB they must be excluded from any criminal investigation - that's unreasonable, and verging on a "pilots covering up for other pilots" position.
PDR