Deepfakes will have the same impact on law enforcement as convincing photoshopped pictures before. Which is to say absolutely no impact.
This comment seems to imply that all court admissible video evidence comes from trusted chains of custody and thereby trusted sources, which isn't necessarily the case.
What's stopping a defense attorney informing a jury about DeepFakes and having that fact factor into their "beyond a reasonable doubt" criterium for criminal cases?
DeepFakes have more potential in PsyOps than legal cases.
So, yes, that information should be given to the jury (as soon as it becomes accurate), and it will lower the potential for false positives (convictions), but with an equal and opposite increase in false negatives.
Is a verbal statement from an impartial witness useless? What if they say recognise the defendant as the criminal they witnessed? Obviously it's not as ideal as unfakable video evidence, but it is useful and has been the basis of legal systems for the millennia before computers and photography arrived.
Fakable video evidence is somewhere between these: you still have to account for the possibility that the person isn't honest, but don't have to worry about the fallibility of human memory.
My daughter's birth certificate could be reproduced 100% indistinguishably by a Fedex Office print shop. But it is backed up by a chain of people who, if necessary, will testify that it is authentic.
People think that testimony requires physical evidence to back it up (look at the reaction to Dr. Ford's accusations). But the legal reality is the opposite... physical evidence is only useful at trial to the extent that credible testimony can establish its authenticity and relevance.
So a deep fake video that looks exactly like a real video will only be useful at trial if it can be established as credible, by the testimony of credible witnesses.
All that said... there is more to life than the justice system. Forgeries have always taken in the gullible, so deep fakes will undoubtedly have a social impact, especially in the early days before the public is generally aware of the capabilities. This is undoubtedly one reason the press is starting to cover this technology so aggressively.
If it's possible to fake HD video, it's also possible to fake grainy surveillance camera footage. If you prove the defendant was in a particular place, and you produce video purportedly from a surveillance camera in that place, a jury would believe it.
And that's not even considering what you can do without an actual forgery, just by messing with context e.g. https://www.buzzfeednews.com/article/meghara/we-had-to-stop-... https://www.nytimes.com/2018/04/21/world/asia/facebook-sri-l...
If "deep fakes" become easier to create than mis-contextified video, they can and will be used to spark conflict in areas with simmering tensions.
I say this as someone actively involved in avoiding the worst case scenarios; I wrote a piece here with more detail: https://www.washingtonpost.com/news/theworldpost/wp/2018/02/... (though HN is not the target audience).
[first paragraph repeated from another comment below]
See the recent SCOTUS nominations for an example.
... and that's in a modern well-educated society.
In countries that are riven by sectarian and tribal rivalries, a convincing video can result in the deaths of millions.
Things will be fine, we'll have a few minor hiccups to resolve, but that will be it.
Some people really underestimate human ingenuity, do you really think that we won't be able to solve this issue in a manner of days if need be? Come on..
We're a few decades away from AI and immortality, and some people are worrying about fucking politics?
Think long term, and chill out.
Also, a fake video of them tearing up a holy book can get them killed.
But yeah, as others have said...I'm more worried about the political and social consequences of doctored videos. We already have a culture that is triggered at the slightest sign of perceived injustice. What if that injustice is a fabricated lie, architected by troll farms?