What should you the attorney do if you suspect undue influence over one of your clients? In order this understand you need to carefully read Vignes v. Weiskopf 42 So.2d 84 (Fla. 1949). In this case the Florida supreme court comments on the responsibility of the attorney who drafted a document while the testator had questionable capacity. The supreme court stated that the attorney was in a catch 22 situation so the attorney's duty was to carefully document all aspects of the meeting(s), and fully apprise the court of the truth of the matter and let the court decide. Thus, here estate planners you have instructions from the supreme court to document fully the meeting with the testatrix/testator and prepare the documents.
Now, that is of course qualified by your professional judgment. An attorney theoretically could be sued for conspiracy if it appears the attorney is helping the proponent of the document and that proponent is not the testator. Further, you as an attorney have a duty to apprise the situation and carefully advise your client on any estate planning options. The point of the Vignes case is that in close cases the attorney has support to fully document the meetings and prepare the documents.