Over the last twenty years, the scholarly field of erroneous convictions has skyrocketed, with multiple articles and books exploring the failures that convict the innocent. However, there has been comparatively little attention to the other side of the coin, failed prosecutions, when the criminal justice system falls short in convicting the likely perpetrator. In this Article, we take up an analysis of failed prosecutions, simultaneously seeking to define its breadth and explain its relation to erroneous convictions. We explore potential hypotheses for the existence of failed prosecutions and then compare those theories to a set of failed prosecutions compiled from a moderately-sized district attorney’s office. With almost no prior research on failed prosecutions, these empirical data help to put meat on the theoretical bones of the concept. In the end, we argue that failed prosecutions and erroneous convictions may be seen as different sides of the same coin of miscarriages-of-justice. Not only do both reflect significant errors by the criminal justice system, but the sources of each also appear to be surprisingly similar.