I don't know if it's still the case in the UK, but in the common law and still in the US this why all substantive evidence, with very rare exception (e.g. dying statements), is witness testimony given on the stand. It may seem absurd when a witness or expert is given a transcript of an earlier statement or report just to recite it, but this is exactly why.

The loophole is all the powers the police and government have to more-or-less punish someone before a trial, or even before charges.

I suspect so. Tbh, I'm surprised it hasn't happened already with the amount of processing that cell phones do on photos, with generative fill/expand/perspective change, etc.

We are quickly going to reach a point where any photo or video taken on a smartphone is inadmissible by default.

There's a big gap between "theoretically unreliable" and courts actually recognizing that, unfortunately. Lots of forensics is much more dubious than CSI would have you believe.

There used to be - probably still are - cameras that would digitally sign all their images. Used in crime scenes? Maybe we will end up seeing wider adoption of this, despite the privacy implications. Hackers attention then will focus (once again) on the certificate supply chain and crypto hardware.

Over all time? Probably tens of millions.

Here in the US? Probably a large double-digit percentage of cases imo…

Consider all of that can be used for forced confessions and forced plea bargains also. In those cases, the "evidence" doesn't even need to exist at all, or be on the record in any way.

Sadly, there's more evil and more laziness/incompetence in the world that's being accelerated by AI than there is good.