Comment by BizarroLand

It depends on the court. Typically evidence is shared with the opposing parties before the court assembles. If there is damning evidence like video of you dancing with the Joker, your side will have an opportunity to preview the video, examine it for being deepfaked, and have a chance to either try to exclude it or possibly will let it slide so that your experts can expose it in trial for being a fake, which could be a strong point in your favor.

From my experience juries are not smart, but if you can show them they've been lied to they will destroy the side that lied to them, not to mention the punishments for lawyers that try to use AI technology to obtain verdicts in their favor by deception.