The burden of proof is on the ones saying it was a true document, not for Trump to prove it wasn't.
Trump has a new explanation for classified documents audio
While speaking with ABC News and Semafor, the former president said his audio clip was "bravado" and that he was not holding a classified document.www.newsweek.com
More. They don't have the document from the sounds of it.
Iran memo not among the 31 records underlying charges in Trump federal indictment
Former President Donald Trump was heard in a July 2021 meeting discussing "highly confidential" information he admitted he could no longer declassify.www.cbsnews.com
There’s no burden of proof issue here, because he’s not charged with dissemination of the documents. The 31 counts pertaining to the documents themselves are for unlawful retention. They don’t need to prove what document he was waving around in that particular interview because the contents or nature of that document don’t constitute an element of any of the counts charged. Remember, they took over 100 classified records back; they’ve only charged 31 of them- likely the ones they could get agreement from the originators to use for court purposes.
The real value of that interview will be showing his mindset, and, particularly his comments showing that he knew he lacked declassification authority post-presidency. That last bit is a powerful contribution to establishing the mens rea of the offences, and pre-emptively slamming the door shut on any attempts he might make to repeat his oft-stated claim that the documents were declassified, or that he had authority to unilaterally declassify them simply by the act of taking them with him out of office. In the text of the indictment, this recording and the interview it took place in are grouped with another similar such event that investigators have testimony on.
Though a sensational news story, this recording is just one small, if bright, tile in the much larger mosaic that is this investigation. Not much on its own, but it bolsters and corroborates other things.
Just updating this line of discussion from a few weeks ago: it appears from para 35 of the new indictment that this specific document that was allegedly shown to a book writer has now been identified, is in the prosecution’s possession, and that they have added an additional charge of wilful retention of defence information (count 32 on the new indictment) pertaining to it. It appears to be a Top Secret//NOFORN presentation. This is the specific document for which there is an audio recording of Trump admitting knowledge that it’s secret and that he did not / could not declassify it. The fact that prosecutors can now close the loop on they specific entire transaction will be helpful to them and will pose a challenge to the defense.