In order to prove that a senior official is legally responsible for atrocities committed by hundreds if not thousands of perpetrators, courts frequently rely on testimonial evidence from percipient, insider, and other witnesses to link crimes with such an official. Accordingly, witness protection is often instrumental to the outcome of a case at the International Criminal Court (ICC) or in a domestic jurisdiction undertaking complementarity proceedings. Recent developments with the Kenya-related cases at the ICC are emblematic of this point. What are the best principles and strategies that judicial institutions can employ to protect witnesses? Do states that support international criminal justice need to revise their laws and policies to better support witness protection issues arising at the ICC and other courts, and how can they be encouraged to do so? Are there alternative evidentiary approaches that can minimize the extent to which criminal courts must rely on potentially vulnerable witnesses?