Evidence law controls what information will be admissible in court and when, how, and by whom it may be presented. It shapes not only the trial decisions of lawyers, judges, and juries, but also many other pretrial and trial decisions and behaviors – for example, by police (whether to initiate a search) and defendants (whether to take a plea deal). Even when the relevant evidence law is known, these decisions are made under great uncertainty. Parties often do not know whether key evidence will be admissible at trial, cannot know how jurors will react to evidence, and, particularly in the criminal context, may not know what evidence their adversary possesses. With all these applications and uncertainties, understanding how legal decisions are made depends on understanding both evidence law itself and the human reasoning processes that created and use it. This chapter thus describes the interplay of evidence law and decision-making across a variety of legal settings and, accordingly, makes frequent references to other chapters in this book.