Possibly, I think "impartial" means reserving the judgement until the judgement is to be made at the end of the trial as opposed to in the middle of the trial, which could very well be wrong - IANAL.
A trial like this is not a single giant evidence dump followed by a giant decision. It is a series of hearings. After each hearing something can be ruled on. You can issue a subpoena to collect more information about A, we have settled B as a fact, you are misreading the law so you have to drop that line of inquiry, etc.
Each hearing is impartial. But impartial decisions come at many points. In fact some points will be appealed to a higher court which will make a ruling and then send it to a lower court again with instructions about how to proceed.
And that's where you're very wrong. Large portions of a trial require judgements to have already been made, even if they've not been written down in a definitive 'judgement' yet. Alsup has made it clear that he's decided that it is a 'matter of fact' that Levandowski stole documents. Now they're arguing over who's responsible and liable.
