Re: Actual case aside
To have (correct) hashes they need to have the actual files too. Which they apparantly don't have.
Whole 'hash' explanation smells very fishy here anyway: There are no un-encrypted files available and encrypted files of course have totally different hashes, so I'm assuming the prosecutors are lying on this.
And they are entitled to do so, also in court: There's not a thing demanding that prosecutor tells the truth, ever.
Only tampering the evidence is illegal, anything else is free game.