[CHY872]

I think you're reading a little too much into that. I think it's worth comparing it to other forms of evidence. It's incredibly common in civil disputes for one party to give untruthful evidence, sometimes out of malice, sometimes simply due to the human psyche (plenty of evidence of people believing falsehoods after all). Likewise, tampering with physical evidence is far from new - tampered photographs have been going around for over a hundred years, while altered financial records and planted drugs are seen in a court somewhere every day. Practically then, the status quo appears to be that if a prosecutor or litigant has done some due diligence and have a good faith evidence based conclusion that the evidence has not been tampered with (by e.g. having the cameraperson swear under oath that the video is an accurate representation of what they saw), then they will be allowed to present it, and that won't change with the proliferation of deepfake video and audio.

At that point the reliability of the evidence may of course be called into question, as with any evidence or witness. The question mark would be whether it was convincing.