The article justifies a standard of proof for crimes against humanity. In order to achieve that objective, this investigation is divided into three parts. Firstly, it reflects the absence of an exhaustive explanation that justifies the application of a standard of proof in transitional justice. Secondly, it adopts an alternative procedural model as a method to set a flexible standard of proof, different from these used in criminal trials. Thirdly, it designs the argument of procedural asymmetries to expose two central aspects: the unjustified disadvantage suffered by the victim of crimes against humanity and the limitations of the legal sanction imposed for these crimes. Lastly, the article concludes that the application of a differentiated standard of proof is only possible in exceptional cases, such as those trials associated with serious human rights violations.