Question: What body has the authority to try all federal impeachments?

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. (US Constitution, Article I, Section 3, Clause 6)

When the English Crown first established the Parliament the king agreed to allow them to be the law-making body of the kingdom. However the King often appointed administrators that were only subject to the King. These administrators were often found to be engaged in such things as bribery, extortion and embezzlement. Finally the Parliament was able to pressure the King into agreeing to give them impeachment power. (Parliament controlled the royal finances.) The House of Commons set the charges and the House of Lords held the trial.

The Founding Fathers used the British model for our Constitution. Thus the House set the charges, representing the people, and the Senate tried the charges, representing the states. They considered the Senate as the appropriate choice for the trial because they had the duty of originally sustaining the presidential appointments. They did not believe that the Supreme Court would be impartial, especially when the President was on trial.