This paper contributes to the interpretation of the standard of proof in criminal trials in two ways. First, it provides a purely utilitarian explanation as to why there are asymmetric costs associated with false convictions and acquittals. It relies on the fact that non-criminals may engage in precautionary activities in order to avoid false convictions. Second, it shows that this difference in the costs associated with false conviction and acquittal rates is under certain circumstances sufficient to justify heightened standards of proofs.