Rarely is it effective advocacy to try to convince the judges that the case law compels them to rule in one's favor. For if that were so, the case probably would not have gotten to the appellate stage (unless it is a criminal case—criminal cases tend to be appealed regardless of the merit of the appeal, because normally the appellant is not bearing the cost of the appeal). And so the second-biggest mistake that appellate advocates make, after exaggerating how much the judges know about, or are willing to devote time to learning about, the circumstances behind the appeal, is to think they can win by rubbing the judges' noses in the precedents. In a case that is not controlled by precedent, the task of the advocate is to convince the judges that the position for which he is contending is the more reasonable one in light of all relevant circumstances, which include but are not exhausted in the case law, the statutory text, and the other conventional materials of legal decision making.
The most effective method of arguing such a case . . . is to identify the purpose behind the relevant legal principle and then show how that purpose would be furthered by a decision in favor of the advocate's position. Having done this, he will have to show that the position does not violate settled law, and this will require a further discussion of the cases. So precedent will enter at two stages in the argument: as a source of governing principles, and as a constraint on efforts to realize those principles in the novel setting of the case at hand. At neither stage, however, will the good advocate be arguing that the result for which he is contending is already "in" the law.
(Richard A. Posner, How Judges Think [Cambridge and London: Harvard University Press, 2008], 220 [ellipsis added])
Keith Burgess-Jackson, J.D., Ph.D. 