There is a strong theoretical argument that there is no sharp distinction between the use of evidence to prove a factual proposition and the use of evidence to persuade a decision maker of the truth of some factual proposition. And there is something -- a great deal, I think -- to the proposition that forcing triers of fact to consider rival claims -- including rival claims about factual matters -- advanced by advocates who have strong incentives to advance rival claims and hypotheses can be a very important device in a society's pursuit of the truth about factual issues. Granting this much, it is still a bit jarring and disconcerting (to me) to receive, from a supposedly reputable publishing company, an advertisement meant for lawyers that proclaims, for example, "Whip the rug out from under opposing witnesses." This headline refers to "'Killer' techniques in Cross-Examination."
Can any system of proof in litigation achieve legitimate purposes if a society sanctions tactics such as "pulling the rug out from under witnesses" by the use of "killer" interrogation methods? I believe that an affirmative answer to this question is possible only because of the ambiguity of the notion of "pulling the rug out from under a witness." If asked, representatives of the publishing company might say, "Well, we were referring to methods of unmasking deception by witnesses." But if they were to say this sort of thing, would you believe them?