How to deal with the tenure case of a colleague who has avoided teaching the classes they were hired to teach? I have a colleague who is coming up for tenure review shortly, and there is a problem with his teaching history.  He was hired to teach classes specifically in area X, although his research is in a slightly different area (Y).  I was on the committee that hired him, and the teaching was a major part of what we were looking for.

However, this person has not taught any classes in area X, at all.  I know from persona knowledge that he requested not to teach X in his first semester, and I have heard from others that he continued to not want to teach in that area.  (I have no reason to doubt the veracity of this hearsay, and his teaching assignment requests can be documented for the tenure and promotion committee.)  This has not turned out to be a serious problem in terms of covering classes.  Somebody else, also from area Y, started teaching some classes in area X, and we later hired a full time person working in Y.

Yet I am still concerned that the assistant professor coming up for tenure has flouted the requirements of the position for which he was hired (which were clearly set forth in his offer letter from the dean).  His research is fine, although not outstanding, and his teaching in other areas would normally be considered adequate.  He also does fine in other considerations (service, collegiality) as well.  However, I am not sure whether it is appropriate to vote in favor of his tenure case, and I was wondering whether what others might think to be appropriate in such a situation.
Based on the information you've provided (and certainly the part of it that is not based on unsubstantiated rumors, which I think it would be quite problematic to take into account), I do not see any cause for concern of a sort that would cast a serious shadow over your colleague's tenure case.

The reason is that individual faculty members do not decide what they teach, but instead the assignment is made by the department (the chair or a dedicated committee) based on its needs, and it is the duty of faculty to teach what they are assigned. It is completely fine if your colleague requested not to teach courses in area X - we all have preferences in such things; it would only not be fine if he were to be assigned such a course and refuse to teach it, and that does not seem to be what happened. If the department can meet its future teaching needs without this person ever teaching a course in area X, why would you or anyone else find fault with that? To summarize, your interpretation that the faculty member "flouted" the teaching requirements of the position seems quite questionable to me, at least in the absence of additional details you haven't provided.

I should add that I have seen cases of faculty members who actively resisted teaching courses they had been assigned. Such conflicts usually involve people with very difficult personalities, and unless the department chair is a total pushover, they will likely escalate quite rapidly to a higher level involving the dean and/or disciplinary action being threatened or pursued. And when this happens, you can be pretty sure that the miscreant is already tenured...