Why, in the US, are politicians tried by other politicians?

Question

If I understand correctly, in the United States, charges are currently being brought against President Trump on the suspicion of enlisting the assistance of foreign governments with re-election, in a procedure called impeachment.

Why does this trial involve politicians?

Firstly, that would seem to violate separation of powers.

Secondly, those deciding on guilt are not neutral.

In a regular trial, a suspect is considered guilty if the jury decides so unanimously. Following a US impeachment, the suspect is considered guilty if 2/3rds of the members of the Senate consider so. It seems reasonable to suspect that Senators may be biased based on their political alignment.

In Israel, Prime Minister Nethanyahu is indicted on the suspicion of corruption, but this trial is run by independent¹ courts, not by fellow politicians. I am aware Israel has a parliamentary system and the USA a presidential system, but I don't see why that makes any difference.

Why are politicians involved in deciding on the guilt of other politicians?

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¹Independent at least in theory. In practice, it always depends on the people.

Answer 1

If I understand correctly, in the United States, charges are currently being brought against President Trump

You understand incorrectly.

It has been asserted that President Trump may have done those things that you mentioned, but he has not yet been charged with anything. There is no criminal proceeding currently taking place in Congress that will result in the President being formally accused of a crime. Impeachment is not a criminal trial, but a political process. Impeachment can be done for any reason Congress can agree upon.

What is taking place in the House of Representatives is an investigative hearing to determine whether or not the President did anything worthy of removing him from office. If the House decides to vote to impeach the President at the conclusion of those hearings, then the Senate has the task of determining whether or not he should be removed from office. This is occasionally referred to as a "trial" but it is not a criminal trial.

If the President were to be removed from office, he would simply no longer be the President or be eligible to be President in the future. Whether he would then be subject to criminal prosecution is a separate question.

Why does this trial involve politicians?

Because it's a political process to determine whether the President should be removed from office, not a trial to determine if he is guilty of a crime and what punishment he should receive under the law.

Firstly, that would seem to violate separation of powers.

No, actually, it does not. Congress is explicitly given this power to check the President. Criminal indictments originate from the Executive Branch, so it would violate separation of powers to immediately treat these sorts of things as routine criminal matters, because the President would have to decide to accuse himself of a crime. The issues with this are the basis of a longstanding opinion in the Justice Department that sitting Presidents cannot be indicted in criminal proceedings while they are President.

Secondly, those deciding on guilt are not neutral.

Guilt is not being decided, merely whether the President should be removed. It is a political question, and is thus best left to people who represent the interests of the people in political questions, e.g. Congress.

In a US impeachment, the suspect is considered guilty if 2/3rds of the members of the Senate consider so. It seems reasonable to suspect that Senators may be biased based on their political alignment.

The political alignment of the Senate is determined by how people voted. Given that this is a political process and not a criminal proceeding, the biased nature of how the proceeding will proceed is a feature and not a bug, because said biased nature is reflective of how people from different parts of the country think about politics. Unlike a jury trial, the Senate's role is not to be the finders of fact in a criminal proceeding.

In Israel, Prime Minister Nethanyahu is indicted on the suspicion of corruption, but this trial is run by independent courts, not by fellow politicians. I am aware Israel has a parliamentary system and the USA a presidential system, but I don't see why that makes any difference

If Benjamin Nethanyahu were President of the United States instead of Prime Minister of Israel, he would need to be impeached before being indicted, because it is understood that the sitting President cannot be indicted, as I stated earlier. I do not know why the opposite situation is the operative one in Israel.

Why are politicians involved in deciding on the guilt of other politicians?

They aren't.

Answer 2

There is no perfect parallel/explanation to give here to someone (e.g. from Germany) who may be used to a parliamentary or semi-presidential system, but...

No confidence votes [...] do not feature in presidential systems, in which the head of the executive government is directly elected by the people and does not rely on the support of the parliament to hold office. The impeachment process in presidential systems differs from no confidence votes in parliamentary systems, in that the grounds for impeachment are confined to serious misbehaviour and abuse of office. In contrast, a no confidence vote may be brought because the majority in parliament no longer supports the executive government, and no specific reason is required.

So on one hand, the impeachment trial is still a matter decided by parliamentarians (Senators in the US case) because it involves removal from a political office (rather than sending someone to prison), but on the other hand it is a more structured approach (in theory) having a higher standard because it is dealing with the removal of an official who was (nearly) directly elected. (And as correctly observed in a comment, the US president is actually elected by an Electoral College.) I say "in theory" because a famous quote often mentioned in this context regarding the official standard of "high crimes and misdemeanors" is that they actually are

whatever a majority of the House of Representatives considers it to be at a given moment in history.

However, removal from office does not preclude a later criminal trial, e.g. for corruption, although in a prior case when this might have happened, namely that of Nixon, who wasn't impeached but resigned under the threat of impeachment, his successor (former vice-president Ford) gave Nixon a pardon [from criminal liability] before a criminal trial could even start; that's also possible in the US system.

Also of note, under the current US DOJ opinion, a sitting president cannot be charged with a crime (in federal and probably state courts as well), so basically impeachment (removal from office) needs to happen first.

(As a couple of interesting trans-Atlantic comparisons, in Germany the president is removed only by a judgement of the Constitutional Court, although it seems either chamber of parliament can bring charges. In France, both chambers of parliament elect from their own membership a High Court that judges the president's removal, which is initiated by a joint resolution of both chambers. In both European countries, the president enjoys immunity from usual criminal prosecution while in office. At least formally, both European countries seem to have stricter formal standards of removal (than the US), although these don't appear to have been tested in practice in either European country. Also, the French and respectively German presidents have less power than the US one [the German has even less than the French].)

Answer 3

The most pithy way to explain is to quote one of the Founders:

Ambition must be made to counteract ambition.

—James Madison, Federalist 51

It was understood that people would attempt to use and abuse the system for self-enrichment, and to otherwise undercut the system and get away with whatever they could. They knew that politicians would be politicians, and not all of them would for all time be so possessed of such sterling character and impeccable morals as to place the ideals of democracy above everything, especially themselves; and that the entirety of the nation would almost surely never agree they are and do as such, even for those who did. They were realists. People were gonna be people. Some of them would be greedy or otherwise not-so-good, and lots of them wouldn't agree with lots of the rest of them.

As such they tried to structure things so that such ambition was a feature, rather than a bug, of the system. In the particular case of Presidential impeachment, the ambitions of a President are balanced by the ambitions of Congress. And I think people on either side of the partisan fence on the current impeachment would claim that's exactly what's going on right now: Republicans are prone to say Democrats are just ambitiously trying to remove a President they don't like and win political points, to our detriment; while Democrats cast essentially the same aspersions at Republicans: they are simply trying to protect their political power and position for their own benefits and at the cost of the nation and constitution. But that one or both sides is pursuing a self-interested plan of ambition, or not, is not a bad thing, as that was the express presumption of the Founding Fathers for how things would work, and was accounted for. The ambitions of a President are intended to be countered by the ambitions of Congressional politicians, and vice versa.

On a more technical level, the constitutional remedy for abuses by the Judiciary is impeachment. It does not make sense to put the control of that power in the hands of the Judiciary, whom it is wielded against. As such it must be wielded by one of the other branches. But the Executive branch is vested in a single person, and giving unilateral authority to a branch over another defeats the purpose of separating and balancing powers. Ergo, the power must belong to Congress. This also serves to pit the ambitions of the political branches against each other.

Answer 4

If I understand correctly, in the United States, charges are currently being brought against President Trump on the suspicion of enlisting the assistance of foreign governments with re-election, in a procedure called impeachment.

There are no charges as the term is commonly understood, i.e. criminal charges. It is an Impeachment, not a criminal trial. Actually, it is not even that; currently, it is an investigation into whether or not to begin Impeachment procedures.

The President is not charged and not tried. The House of Representatives is investigating whether to start the process of Impeachment, which is a political process to remove the President from the political Office of the President because he is deemed politically unfit.

Why does this trial involve politicians?

It is not a trial. It is a political process.

Firstly, that would seem to violate separation of powers.

Charges are brought by the Executive Branch. The President is the (Head of the) Executive Branch. He would effectively have to charge himself.

As mentioned in the comments, this process is part of the Checks and Balances, and thus it is the exact opposite of Separation of Powers by design.

Secondly, those deciding on guilt are not neutral.

They are not deciding on guilt. They are deciding on political fitness to hold the Office of President.

In a regular trial, a suspect is considered guilty if the jury decides so unanimously. Following a US impeachment, the suspect is considered guilty if 2/3rds of the members of the Senate consider so. It seems reasonable to suspect that Senators may be biased based on their political alignment.

The President is neither a suspect nor will he be found guilty. He may or may not be found politically unfit to hold the Office of President. He will not be fined, he will not be put in prison, he will simply stop being President.

In Israel, Prime Minister Nethanyahu is indicted on the suspicion of corruption, but this trial is run by independent courts, not by fellow politicians. I am aware Israel has a parliamentary system and the USA a presidential system, but I don't see why that makes any difference.

The difference is that Israeli Prime Minister Netanyahu is indicted and tried, whereas President Trump is not.

Again, currently, the House is still in the process of investigating whether or not to even begin the process of Impeachment. But even if they were already in the Impeachment process, it would still not be a trial, and President Trump would still not be indicted.

Why are politicians involved in deciding on the guilt of other politicians?

They aren't. They are involved in deciding political fitness for Office of the President. Or, rather, they are currently involved in investigating whether or not to start that process.

Note that there is a veeeeery remotely related process in Germany: Members of Parliament enjoy Parliamentary Immunity from Prosecution. This Immunity can only be revoked by Parliament. So, in some very remote sense, also in Germany, politicians are involved in "deciding the guilt of other politicians". Of course, again, they don't actually decide the guilt, they only decide whether or not to make it possible for the Executive and Judicial Branch to determine the guilt of a member of the Legislative Branch.

Answer 5

The President is the head of the executive branch. The head of the judicial branch, the Chief Justice assists with the trial. The third and final branch, the legislative branch is involved by bringing charges and voting on removal or censure or whatever fits.

All three branches are involved, so separation of powers is very much observed.

You are correct that the people who vote in the Senate may not be neutral. However, if the other branches were not involved, that would mean that the could not place checks upon each other. The executive branch would not have to answer to Congress without that.

You can argue that it should work differently, but that is opinion on either side of the argument.