Question: What did Thomas Jefferson see as a major flaw in the judicial system under the Constitution?

It is not enough that honest men are appointed judges. All know the influence of interest on the mind of man, and how unconsciously his judgment is warped by that influence. To this bias add that of the esprit de corps, of their peculiar maxim and creed that 'it is the office of a good judge to enlarge his jurisdiction,' and the absence of responsibility, and how can we expect impartial decision between the General government, of which they are themselves so eminent a part, and an individual state from which they have nothing to hope or fear?
(Thomas Jefferson: Autobiography, 1821. ME 1:121)

We have... [required] a vote of two-thirds in one of the Houses for removing a judge; a vote so impossible where any defense is made before men of ordinary prejudices and passions, that our judges are effectually independent of the nation. But this ought not to be. I would not indeed make them dependent on the Executive authority, as they formerly were in England; but I deem it indispensable to the continuance of this government that they should be submitted to some practical and impartial control, and that this, to be impartial, must be compounded of a mixture of state and federal authorities.
(Thomas Jefferson: Autobiography, 1821. ME 1:120)