This paper addresses the selective mechanisms by which criminal proceedings produce strong arguments. It does so by focusing on the failing of argument themes (topoi) in the course of criminal proceedings, rather than on their career. In a further step, the notion of failing is bound to learning: different forms of failing point at different ways and places of learning. The study is comparative, relating cases from four different legal regimes (England, USA, Italy and Germany) that are taken from four extensive ethnographic studies in defense lawyer's firms. We will track down the failures of topoi at three different stages (pre-trial, trial, and deliberation) in our different legal regimes. Failing occurs in all proceedings in various modes and at different stages. We argue that those modes as well as the different stages at which they occur point at the spots in the respective procedures that allow for learning about the inherent conceptions of "good reasons."