I'm again impressed that you offer a real argument.
Golfing Gator this is how you yourself used to debate before Trump Derangement got the better of you. I hope you'll snap out of it soon.
Two answers:
1) Trump would not have to prove he declassified the documents. He would only need to raise reasonable doubt that they were still classified.
2) that assumes there would ever be a trial. I doubt the DOJ wants a trial. They're not that stupid. I believe that their goal is for Garland to pull a well-timed Comey on Trump by announcing announcing no prosecution after a lengthy recitation of his supposed crimes. That way they can assassinate his character without his having a chance to defend himself.
It was foul when Comey did that to Hillary and Trump was right to fire him for it.
That's their position but I doubt it is what they believe. To a lawyer, that isn't lying, its advocating.