On 7 March 2014, Trial Chamber II of the International Criminal Court (ICC) convicted Germain Katanga for war crimes and crimes against humanity. Katanga's conviction is based on the concept of common purpose liability as regulated in Article 25(3)(d) of the Rome Statute. This liability theory establishes criminal responsibility for wilfully or knowingly contributing to the crimes of a group of persons who act together pursuant to a common purpose. The ICC regards common purpose liability as a residual liability theory, which provides for a lower level of blameworthiness than principal forms of criminal responsibility, such as joint perpetration. This article appraises the residual and inferior status of common purpose liability by comparing the ICC's application of common purpose liability and joint perpetration. The comparison makes clear that common purpose liability in theory stipulates lower actus reus and mens rea standards than joint perpetration. However, in practice the ICC applies the requirements of both these liability theories in a context-dependent way in interplay with the particular facts of individual cases. It can therefore not be concluded in general terms that common purpose liability by definition constitutes a less serious type of criminal responsibility than joint perpetration. Instead, it is preferable to adopt a flexible approach, which recognizes that common purpose liability covers a variety of conduct entailing different levels of blameworthiness.