I was wondering this today. Why did the founding fathers make it so the highest court of the land preside over impeachment hearings instead of politicians?
Is there a good reason for this and has this ever been looked at being changed?
This is defined in Article 1, Section 3 of the Constitution:
The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.
Specifically, it's not the whole SCOTUS, currently comprised of nine justices, but rather the chief justice of the United States who presides. The chief justice holds the highest rank, if you will, of anyone in the judicial branch, and is thus expected to have the best command of legal proceedings, although the exact nature of how the Senate conducts the impeachment trial is not spelled out in the Constitution. I wrote more about impeachment here, and there's some activity in the comments as well.