Related, it would be interesting to understand why decision makers aren't held to similar standards as a traditional jury. Are there costs/benefits we've weighed as a nation, such that this is the logical outcome? For example, if a juror were to indicate their opinion in advance, they would likely be disqualified from serving. Also, it's not obvious to me that the public can trace a jury trial's outcome back to each juror's independent vote, right?
Hi there, we ran an impeachment explainer awhile back that may answer some of your questions. The short version of this is that impeachment is a political process, and rules of evidence and due process that apply to civil and criminal cases do not apply in the Senate. To quote from that older piece:
in Federalist no. 65, Alexander Hamilton described the process as such:
A well-constituted court for the trial of impeachments is an object not more to be desired than difficult to be obtained in a government wholly elective. The subjects of its jurisdiction are those offenses which proceed from the misconduct of public men, or, in other words, from the abuse or violation of some public trust. They are of a nature which may with peculiar propriety be denominated POLITICAL, as they relate chiefly to injuries done immediately to the society itself.
Impeachment itself is inherently is a political process that courts won't get involved in. (Nixon v. United States, 506 U.S. 224 (1993) -- no, not that Nixon, a judge named Nixon.)
So what that means is that a vote to convict that would lead to removal from office (a moot point here) or preventing an impeached official from serving again, is not a jury trial type of vote; it's a political vote on a political process.