the application by the police for access to evidence held by AAIB
With my very modest understanding of investigative matters, I understand that both the AAIB and the police are to act within their mandates and to act in the interest of the public. And there's only one "the public" as I see it. Therefore, ultimately though perhaps approached from different directions, I would hope that the single public interest can be defined, and supported in the efforts of both entities.
The AAIB meets the public interest while not appointing blame. The police support the greater public interest of investigating events which might have a criminal offense involved, while maintaining that innocence exists unless guilt is proven.
The public interest is not, or less met, if safety is not advanced, if innocent persons are falsely prosecuted, or if people guilty of an offense against law are overlooked.