It comes up in descriptions of the three branches. The challenges come from Brutus, and in #11 he takes on the Judiciary, pointing out there are no safeguards against the courts. That comes up in a few weeks.
Our Framers intended impeachment and the “Exceptions and under such Regulations” clauses to provide ample checks.
Fault does not rest with the Constitution when, for instance, the anti-constitutionalists Kagan and Sotomayor were permitted to turn their Senate hearings into farcical embarrassments.