In This Article Expand or collapse the "in this article" section Complicity in International Criminal Law

  • Introduction
  • General Overviews
  • Historical Roots
  • Domestic Law
  • Complicity and Sentencing
  • Philosophical Foundations
  • Complicity in International Law: A Multifaceted View
  • Critical Scholarship

International Law Complicity in International Criminal Law
Marina Aksenova
  • LAST REVIEWED: 24 February 2021
  • LAST MODIFIED: 30 March 2017
  • DOI: 10.1093/obo/9780199796953-0152


Complicity is a doctrine that attributes criminal responsibility to those who are involved with but do not physically perpetrate a crime. Despite the seeming simplicity of this definition, complicity is a highly complex and contentious concept in domestic and international criminal law alike. Its function is to construct a link between the accomplice and the criminal act of another person. This is not an easy task if one accepts the distinct moral importance of the perpetrator’s role. The matter is further complicated if the crimes are committed in the context of ongoing violence involving many actors at different levels of state hierarchy—international criminal law typically tackles this scenario. Complicity goes to the heart of the discipline’s quest for balance between the accused’s individual contribution and the collective nature of mass offending. The principle of legality demands that there exists a well-defined link between the crime and the person charged with it. This is so even in the context of international offending, which often implies “several degrees of separation” between the direct perpetrator and the person who authorizes the atrocity. How to construct this link without jeopardizing the interests of justice? Different forms of complicity, such as aiding and abetting or instigating, are firmly rooted in domestic legal systems and rather accurately capture the input of each accused. This contrasts with the newly developed concepts of joint criminal enterprise (JCE) and (in)direct co-perpetration, oriented toward joint participation. While complicity has more domestic law grounding than some other modes of liability, its focus on individual contributions to the crime calls for enhanced scrutiny. This feature of complicity also creates inevitable evidentiary challenges for international prosecutors.

General Overviews

This section presents three types of works essential for understanding of complicity in international criminal law—general authoritative textbooks on international criminal law such as Cassese 2008, Ambos 2013, O’Keefe 2016, and Cryer, et al. 2010; specialized volumes dealing with the modes of liability such as van Sliedregt 2012 and Boas, et al. 2007; and two monographs dealing with complicity in international criminal law: Aksenova 2016 and Jackson 2015. All these books attest to the fact that a single simple formula for secondary participation in international criminal law is not feasible because various forms of complicity, once applied to the facts of a case, present some challenges. Each form of complicity requires careful stipulation of its constitutive elements—the conduct requirement and the fault requirement. In the literature and case law these elements are often referred to as actus reus and mens rea (this terminology, however, creates some confusion with actus rea reus and mens rea of the respective substantive crime). The key to the successful application of different forms of complicity is a careful balancing of its different elements from the facts of the case: in instances when the accomplice is in the physical proximity to the unfolding atrocities, his culpability may be inferred from the surrounding circumstances, while his contribution to the crime needs to be spelled out in detail—mere presence at the scene is not sufficient to attract criminal responsibility. In cases where the accomplice is removed from the principal perpetrator—in time or in space—the emphasis should be on the accomplice’s guilty state of mind. The following works elaborate in detail on the typology of complicity and its constitutive elements as discussed in the case law of the ad hoc tribunals—the International Criminal Tribunal for the former Yugoslavia (ICTY) and the International Criminal Tribunal for Rwanda (ICTR)—the Extraordinary Chambers in the Courts of Cambodia (ECCC), the Special Tribunal for Lebanon (STL), the Special Court for Sierra Leone (SCSL), and the International Criminal Court (ICC). These books also problematize the topic and offer an in-depth analysis of the historical roots and the theoretical foundations of various liability modes in international criminal law.

  • Aksenova, M. Complicity in International Criminal Law. Oxford: Hart, 2016.

    This monograph provides an overall comprehensive treatment of complicity within the discipline of international criminal law and beyond. It focuses on the case law of the ad hoc tribunals, hybrid courts, and the ICC, explaining the constituent elements of different forms of complicity. In addition to that, the book covers the correlation of complicity and sentencing, compares complicity in the law of state responsibility and international criminal law, and discovers its domestic law origins.

  • Ambos, K. Treatise on International Criminal Law: Foundations and General Part. Vol. 1. Oxford: Oxford University Press, 2013.

    DOI: 10.1093/law/9780199657926.001.0001

    This volume focuses on the general principles of international criminal law with a particular emphasis on the principle of individual criminal responsibility. The author skillfully places it within the general structure of the discipline.

  • Boas, G., J. L. Bischoff, and N. L. Reid. International Criminal Law Practitioner Library International Criminal Procedure: Forms of Responsibility in International Criminal Law. Vol. 1. Cambridge, UK: Cambridge University Press, 2007.

    This book aims at practitioners, hence its clarity and relative simplicity. It comprehensively covers all forms of responsibility as defined in the jurisprudence of the ad hoc tribunals and hybrid courts. A large part of the volume focuses on the concept of the joint criminal enterprise, which was possibly the most contentious mode of liability in the case law of the ad hoc tribunals.

  • Cassese, A. International Criminal Law. 2d ed. Oxford: Oxford University Press, 2008.

    Cassese’s International Criminal Law is the most popular textbook in this field. It provides a clear and authoritative account of the main substantive and procedural issues. Section 2 of the book is devoted entirely to the modes of liability.

  • Cryer, R., H. Friman, D. Robinson, and E. Wilmeshurst. An Introduction to International Criminal Law and Procedure. 2d ed. Cambridge, UK: Cambridge University Press, 2010.

    DOI: 10.1017/CBO9780511760808

    This is a well-balanced and easy-to-follow textbook on international criminal law that provides a detailed overview of the discipline with sufficient level of detail. Chapter 15 deals with the general principles of liability, including a discussion of the various forms of complicity.

  • Jackson, M. Complicity in International Law. Oxford: Oxford University Press, 2015.

    DOI: 10.1093/acprof:oso/9780198736936.001.0001

    This monograph focuses on complicity in international criminal law and the law of state responsibility, thereby excluding complicity of corporations and international organizations. In these two areas, the aim is not to provide a comprehensive treatment of complicity but rather understand how international law prohibits state and individual complicity by developing an analytical framework for discussing the issue.

  • Mettraux, G. International Criminal and Ad Hoc Tribunals. Oxford: Oxford University Press, 2005.

    Mettraux’s volume is a thorough but succinct analysis of the jurisprudence of the ad hoc tribunals. It is a good entry point to the study of the modes of liability as developed by the ICTY and ICTR.

  • O’Keefe, R. International Criminal Law. Oxford: Oxford University Press, 2016.

    O’Keefe’s volume is a thorough but succinct state-of-the-art analysis of international criminal law. The author provides a helpful description of the modes of responsibility in conjunction with both treaty- and custom-based crimes under international law.

  • van Sliedregt, E. Individual Criminal Responsibility in International Law. Oxford: Oxford University Press, 2012.

    Van Sliedregt’s book is the most comprehensive treatment of the principle of individual criminal responsibility in international criminal law. She maps out the different modes of liability as developed by the ad hoc tribunals, hybrid courts, and the ICC. This work is essential in understanding the constituent elements of each form of complicity, the historical evolution of the principles regulating the attribution of blame in international criminal law.

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