Abstract
While defendants can always appeal convictions in trial, public prosecutors often face prohibition of appealing acquittals. This asymmetry twists the crim- inal procedure towards the interests of defendants. The paper first inquires the impact of asymmetrical appeal powers on the number of convictions, acquit- tals and errors of type I and type II. It then surveys the traditional justifica- tions of asymmetric appeal powers. Finally it frames pro-defendant proce- dural safeguards, such as asymmetric appeal powers, into the Blackstonian precept that it is “better that ten guilty escape than that one innocent should suffer”.