It is perhaps unfortunate, but some of the things Donald Trump is accused of could require the prosecutors to prove he knew that he was breaking the law. If he thought he was trying to rescue an election he genuinely believed he won, he could get off. Likewise, if he thought as a former president he was legally entitled to hang on to top-secret documents because he was never formally put on some kind of trial and had his security clearance taken away by force, he might be found not guilty. So a lot depends on what was going on in his mind, a tough thing for prosecutors to prove. Nevertheless, it can be done.
For example, in the D.C. conspiracy case, the indictment alleges that Trump made "knowingly false" claims of election fraud. How can a jury be convinced about the "knowingly" part? Well, there are witnesses. Cassidy Hutchinson could testify that her former boss, Mark Meadows, told her that Trump had told him he lost. That is second-hand testimony (hearsay, and thus inadmissible), but she put it on the record during the Jan. 6 hearings. Meadows can be called to the stand and asked point blank if: (1) he told her that and (2) Trump told him that he knew he lost. Meadows is an eyewitness and thus can be forced to testify. At this point, it is unlikely that he wants to add perjury to all the other charges he is facing.
Also from the evidence already public, and probably a lot that is not public, it is abundantly clear that Trump didn't care about the facts. There is a legal doctrine that says that when a defendant made a conscious effort to avoid "knowing" the law or facts, the judge can instruct the jury to act as if he in fact "knew," since the effort of actively trying to avoid "knowing" indicates that he knew "knowing" would make his act criminal. It is called willful ignorance. There is a lot of evidence out there showing that he tried hard to avoid knowing, to wit:
And this is only a fraction of the things publicly known. Special Counsel Jack Smith has interviewed hundreds of witnesses and probably has testimony from others who heard Trump say he lost but wanted to fight on anyway. Trump also knew that he lost 61 lawsuits about election fraud, so the courts looked at it closely and concluded there wasn't any significant fraud. Attorney John Lauro is going to have his hands full in the D.C. case.
In the Mar-a-Lago documents case, the IT guy, Yuscil Taveras, has signed a cooperation agreement and will testify that he was ordered to wipe the surveillance server of the recordings of boxes of documents being moved around. He didn't get the order directly from Trump, but can implicate his direct boss in the crime of trying to destroy evidence. We're waiting for the direct boss to flip as well. It probably won't be long. (V)