It seems no Republican politicians have ever sat on a grand jury, which is the equivalent of an impeachment inquiry.
Defense does not enter into a grand jury proceeding. The crime of which a defendant is accused is explained with reference to actual law. Evidence is presented. Witnesses give testimony. The defense has no right to learn what is said or who said what _ that is what is meant by “sealed”. At the end, a majority (not everyone) in the jury must decide it is proper to bring an indictment and continue to trial.
Only at trial is evidence presented publicly, and witnesses revealed.
The only difference between a grand jury and an impeachment inquiry is that the law in question is loosely defined.
Republicans, however, pretend this is actually a secret trial. They claim that any witness testimony is “hearsay,” that videos and documents are falsified, that interpretations of confessions are open to question. “Yes, I did that, so what,” becomes “Of course I did not do that.” And that “high crimes and misdemeanors” is meaningless short of actual murder (in spite of the impeachment of another president for fibbing about consensual sex.) Such was obviously not the intent of the clause, or crimes would have been further specified directly.
For those of us who been on a grand jury, all this is crystal clear. But nobody ever accused politicians _ even lawyers _ of being particularly well educated even in the basic traditions of our democracy and legal system.