Who will benefit and who will suffer from a legal decision-maker’s doubts? Since a tie-verdict is not possible in law, decision-makers must resolve their doubts in one direction or the other, and burdens of proof, standards of proof and presumptions govern this process. Together they design the obstacle course through which a party’s case will move on its way to the finish-line. By making this party’s job easier or harder, they reflect an underlying judgment about which kind of mistake is worse: a mistake in her favour or a mistake at her expense. While legal scholarship typically imagines that this judgment results from a rational calculus, this book suggests that it often reflects, instead, a desire to avoid a particularly salient kind of harm, as illustrated through a comparative study of criminal and civil law in common law jurisdictions.