Our justice system worked for a very long time in an environment where cell phones didn't exist, where cities weren't covered end-to-end in CCTV cameras, and our courts were able to do a decent job of protecting the innocent and putting away the bad guys. Distrust of video evidence only makes us revert back 30 years to when we weren't so monitored. It's something that we can survive. On the other hand, if we don't see an outright rejection of deepfakes in our courts, we're going to see it used as a political weapon. We can survive the former, but not the latter.
Unfortunately, I don't see it working out that way. Once courts and police get their hands on a new technology and it becomes sufficiently ingrained, it doesn't matter how little sense it makes. Drug dogs are bullshit, but they're still everywhere. [1] DNA evidence can be synthesized and planted, but it's the gold standard in terms of courtroom evidence. [2]
Given all of this, I don't have a lot of faith in our justice system getting deepfakes right, and that worries me a lot more than guilty people being presumed innocent.
[1]: https://www.washingtonpost.com/opinions/2019/02/05/supreme-c...
[2]: Good reason to avoid giving your DNA to 23andMe or to the state. Unfortunately, both my parents did 23andMe, so I'm screwed regardless. https://www.nytimes.com/2009/08/18/science/18dna.html