Videos are easy enough to spot as fakes for now, but I've heard really convincing AI audio fakes. Audio only recordings might not be usable as evidence without additional confirmation of authenticity.
Are audio/video recordings I take with my phone going to be useless in a decade because deepfakes are virtually indistinguishable and there is no "additional confirmation"?
Point being, it'll take more than just looking at the source image/video/audio for signs of AI manipulation, because soon enough, all recordings will be AI-manipulated before even hitting persistent storage.
In other words: everything will be deepfake by default, and the issue will turn into telling which deepfakes were done to lie about substantial aspects of reality pertinent to the case, and which ones were made to enhance some non-relevant qualities (aesthetics, compressibility, etc.).
Lots of ways to sign photos and videos today that should make them fully verifiable in the future (assuming public/private key cryptography remains secure). For stuff that isn't signed, it's not like good old detective work can't verify in a lot of cases. Phone records, eye witnesses, additional unpublished recordings, etc.
Also being verified really only matters when it comes to "truth" as defined by law. It's not like your family won't enjoy your videos of Christmas '23.