In court, on impeaching expert testimony: Imagine that Einstein is still alive, that he hadn't done anything since he actually died, that he was never famous (so no one in a modern courtroom except for two lawyers knows who he is), and that the world's knowledge of relativity had not changed since he actually died. At someone else's trial, he testifies on relativity as an expert. Answering questions, he explains both his special and general theories in terms a jury understands. Counsel thanks him. Opposing counsel in cross-examination asks Einstein if his theory includes a "cosmological constant". Einstein testifies firmly: "No." Opposing counsel reads to the court from an earlier publication by Einstein that there is a cosmological constant. Einstein seems urgently about to say something but the judge reminds him that he may only answer questions he is asked and no questions are pending at the moment. Opposing counsel has no further questions, counsel who brought Einstein does not seek to ask anything (perhaps because not expecting this turn of events) and the witness is dismissed. Someone searching history would find that Einstein had publicly said that the cosmological constant was the "biggest blunder of his life", but a jury is not allowed to do outside research before issuing its verdict and this is not a nonjury trial. I understand that impeachment frequently works to persuade a trier of fact to disregard impeached testimony; assume such persuasiveness succeeds in this case.
I think this illustrates an inadequacy of the system of determining the state of scholarship through expert testimony, among other reasons because it discourages bringing an expert who might ever have published a statement they would later dispute, and that would exclude most research scholars with long publication histories. Am I legally wrong about this hypothetical Einstein being easily impeachable? Does this vary much by jurisdiction of place?
I'm not opening a debate on reform, just trying to see if I misunderstand the general law.