Layering is hard, but a deep fake would somehow have to fool your opponents as well as the Court. Evidence has to be validated by witness testimony.
If a fake recording relates to someone involved in the case, then the opposing party should know it is fake and be able to prove it.
One can imagine a situation where a party presents exculpatory evidence involving only third parties, but the othrr side should demand all meta data that relates to the production of the evidence.
I faced this issue years ago with a surprise computer file that turned up in discovery. First I had to explain to the judge what meta data was, and then I had to convince her I needed it and that it would not be difficult to provide.
Eventually we proved the document had been created recently and back dated a couple years. Settlement ensued.