From Chapter VII, titled “Illegal Judges,” of Lysander Spooner’s Essay on the Trial by Jury:
It is a principle of Magna Carta, and therefore of the trial by jury, (for all parts of Magna Carta must be construed together,) that no judge or other officer appointed by the king, shall preside in jury trials, in criminal cases, or “pleas of the crown.”
This provision is contained in the great charters of both John and Henry, and is second in importance only to the provision guaranteeing the trial by jury, of which it is really a part. Consequently, without the observance of this prohibition, there can be no genuine or legal that is, common law trial by jury. At the common law, all officers who held jury trials, whether in civil or criminal cases, were chosen by the people.
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We can all perhaps form some idea, though few of us will be likely to form any adequate idea, of what a different thing the trial by jury would have been in practice, and of what would have been the difference to the liberties of England, for five hundred years last past, had this prohibition of Magna Carta, upon the king’s officers sitting in the trial of criminal cases, been observed.
The principle of this chapter of Magna Carta, as applicable to the governments of the United States of America, forbids that any officer appointed either by the executive or legislative power, or dependent upon them for their salaries, or responsible to them by impeachment, should preside over a jury in criminal trials. To have the trial a legal (that is, a common law) and true trial by jury, the presiding officers must be chosen by the people, and be entirely free from all dependence upon, and all accountability to, the executive and legislative branches of the government.