Aside from the current political environment, it’s helpful to think of impeachment as accusation. With enough votes a person can formally be accused, i.e. impeached. Whether that person can then be convicted of that accusation is entirely another matter, as we have seen in recent years. So, as everyone seems to be saying in their responses, yes, a judge can be impeached for a number of (not enumerated) acts, the test is whether the Senate would uphold that accusation. And, as Procrustus says, it’s not lying, i.e. perjury, if you simply change your views.
I agree with all you wrote, except perhaps this. If a jury is convinced by what he said despite what she said (or vice versa) then they can convict. I’m not aware of any requirement for a higher standard of proof. (compare treason: “No Person shall be convicted of Treason unless on the testimony of two Witnesses to the same overt Act, or on Confession in open Court.”)
Treating this as a hypothetical matter, I’d say the answer is clearly yes.
First, there is no clearly defined standard for what constituted impeachable behavior. So in real world terms, a Justice can be impeached for pretty much anything if the political situation makes it possible.
Second, I feel this particular charge would be reasonable ground for an impeachment, even if there weren’t political issues involved. The Senate has the constitutional duty to review judicial candidates before voting on their confirmation. If the candidate provides false information to the Senate, they are subverting the process and thereby rendering their confirmation invalid. Impeachment in such a case would be reversing what has been found to be an invalid confirmation.
Third, there is the nature of the job. A Supreme Court Justice is one of the highest legal authorities in the country. Committing perjury is a substantial breach of the legal system. A person who was willing to do this is unfit to hold that high legal authority.
On this specific issue, you would probably not be able to meet a standard of perjury. To show perjury, you would have to show that the nominee knew he was lying at the time he was testifying. His defense would be that he meant what he said when he was testifying but later changed his views.
In general, perjury requires a higher bar. IIRC, the rule of thumb for persecuting perjury is two independent items proving the offense, that the assertion under oath was deliberately not true. (Not sure if it’s codified in law).
Obviously in almost any case, “beyond reasonable doubt” means there is more evidence pointing to the guilty party than just the contradictory word of another. (except maybe in cases against minorities). I.e. to convict someone of murder you would need more evidence than absolutely nothing else but “he told me he did it.”
this is why so many rape cases are difficult to prosecute, since they can sometimes hinge on two conflicting accounts, only one of which can be true, without definitive independent corroboration about consent. Civil cases don’t need such a high bar for a decision.