Looking ahead to an impeachment trial and the conflict it sets up between Roberts & McConnell - 2019-11-25
A motion 'in limine' is a trial motion to limit or exclude certain testimony or evidence, and the judge, in deciding what the jury can hear, considers how relevant that evidence is to the proceeding versus the potential likelihood that the evidence will prejudice the jury.
Impeachments aren't trials, but I suspect that the rough impeachment equivalent of a motion in limine, in whatever form it takes, will be the key to the impeachment trial, and that the same relevancy vs. prejudice balancing test will guide the Chief Justice when the impeachment inquiry moves over to the Senate and becomes a trial.
The House has already fought over admissibility, the most obvious example being Hunter Biden, whose testimony Adam Schiff found not at all relevant but whom Devin Nunes believes is the only necessary witness. Of course, the Dem majority controlled the inquiry phase and so Biden wasn't subpoenaed.