The New Hampshire Constitution, I just learned, provides:
It is the right of every citizen to be tried by judges as impartial as the lot of humanity will admit. It is therefore not only the best policy, but for the security of the rights of the people, that the judges of the supreme judicial court should hold their offices so long as they behave well; subject, however, to such limitations, on account of age, as may be provided by the constitution of the state; and that they should have honorable salaries, ascertained and established by standing laws.
The Massachusetts Constitution is very similar:
It is the right of every citizen to be tried by judges as free, impartial and independent as the lot of humanity will admit. It is, therefore, not only the best policy, but for the security of the rights of the people, and of every citizen, that the judges of the supreme judicial court should hold their offices as long as they behave themselves well; and that they should have honorable salaries ascertained and established by standing laws.
“As impartial as the lot of humanity will admit” — that’s a pretty demanding standard, if taken literally (and I doubt that it is).