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Historically, the commission of genocidal offenses has involved large numbers of perpetrators, whose contributions varied greatly with respect to both form and intensity. From a legal perspective, attributions of criminal responsibility to the involved parties does not mean that the overall responsibility for genocidal acts is somehow divided among them. Each individual involved in genocidal conduct bears responsibility for his or her conduct, and the attribution of individual guilt is organized pursuant to a set of recognized forms of participation. Those who participate in the commission of a genocidal act in accordance with one of those prescribed forms incur responsibility for their conduct.

One form of participation is "complicity" in genocide, pursuant to Article III(e) of the United Nations (UN) Convention on the Prevention and Punishment of the Crime of Genocide (Genocide Convention). Due in part to the word's terminological ambiguity and its slightly different connotation in several legal environments, the exact meaning of the word in the context of genocide is still subject to much debate, notably that taking place in the ad hoc tribunals for the former Yugoslavia and for Rwanda, and this ambiguity has yielded contradictory interpretations in existing case law.

What is certain is that an individual may be regarded as an accomplice in genocide if it is established that he or she deliberately provided practical assistance, encouragement, or moral support that had a substantial effect on the perpetration of the crime. This forms the minimum standard that a person who has contributed to the commission of the crime must meet if he is to be held responsible for complicity in genocide. His or her acts may take many forms, and the contribution of each accomplice may differ vastly in terms of its gravity. His contribution need not be an indispensable condition to the commission of the crime by the principal offender, but neither can it be entirely innocuous, in that it must have "substantially affected" the commission of the crime. Such complicity may in principle take place before, during, or after the time of the actions of the principal offender. Mere presence at the scene of the crime may, under certain circumstances, be sufficient to qualify as complicity (as, for instance, when such presence may be shown to provide encouragement to the principal offender, or when the individual present had a duty to intervene and failed to do so). So could acts of encouragement or assistance such as transporting executioners to killing sites, identifying members of the targeted group, providing forces and ammunition for the killings, and other forms of aiding and abetting the commission of the crime. The only form of complicity in the context of genocide that appears to have been criminalized, however, is complicity in genocide itself. Complicity in other acts that are related to genocide, such as "conspiracy to commit genocide" or "direct and public incitement to commit genocide," is not regarded as a discrete basis for criminal liability.

It has been suggested in a number of legal decisions that accomplice liability is limited to individuals who, from a hierarchical point of view, are lesser participants, whereas liability for genocide proper is reserved for high-level officials, which reasoning would create a division between the "planners," who would generally be principals to genocide, and "executioners," who would generally be mere accomplices to such crimes. Such a view does not appear to be supported in international criminal law. Anyone, regardless of rank or status, could in principle be found guilty of complicity in genocide, as well as of genocide itself. The law of genocide, as it stands, does not support any suggestion that different forms of liability have been assigned according to the different hierarchical levels of accused persons. What matters in respect of accomplice liability is the nature of the actions or omissions of an accused person, not his or her position within a hierarchy.

It is yet unclear whether, in order to be held responsible as an accomplice to genocide, an individual must possess the requisite genocidal mens rea (intent), or whether it is sufficient that he or she knows of the genocidal intent of those whom he or she assists. It would appear that the pivotal element of the crime of genocide is this very element of intent, and that genocidal intent should be required of each and every participant (in the establishment of his or her guilt) in a genocidal offense, including accomplices. One would therefore be found responsible for complicity in genocide only if the prosecution were able to establish that the accused possessed the requisite special intent (as opposed to his or her mere knowing of the principal offender's intent). In the absence of genocidal intent on the part of the accomplice, actus reus (action) of that accomplice, whatever its degree of atrocity and however similar it might be to the acts described in the Genocide Convention, could not be regarded as genocidal. The distinction between one who commits a genocidal crime and one who is merely an accomplice to it would thus depend on the motivational aspects of their respective contributions to the crime. It is important to note that, in that respect, the sentence imposed on an individual involved in a genocide would not be based primarily, if at all, on the legal classification of his conduct as commission rather than complicity, but would depend on the gravity of his conduct—so that an accomplice could theoretically receive a heavier sentence than a principle.

Complicity in genocide as a form of participation is not freestanding, in that it can only exist when there is a punishable principal act in which the accomplice could be complicit. Consequently, it must be proven that the crime of genocide has indeed been committed before liability for complicity may attach to a lesser participant in this crime. However, the principal offender need not have been prosecuted or convicted, and he need not even have been identified.

Complicity in genocide is sometimes understood in a broader, less technical, sense than the one expounded above, whereby one may be regarded as an accomplice to genocide if one has participated in the commission of a genocidal act in a form criminalized under international law but not explicitly under the Genocide Convention. The ad hoc tribunals for the former Yugoslavia and for Rwanda have recognized, for instance, that criminal liability for genocidal actions is not limited to those who have participated in the commission of these actions in one of the forms provided for under the Genocide Convention, but that other forms of participation are criminalized under customary international law. Two such forms of criminal participation deserve particular attention here: command, or superior, responsibility and joint criminal enterprise or common purpose doctrine.

Command, or Superior, Responsibility and Genocide

A superior—civilian or military—may under certain circumstances be held criminally responsible for the acts of his subordinates, or, to be more precise, for failing to prevent or punish his crimes. Drawing on the jurisprudence of court decisions that date back to World War II (and of later court decisions), the ad hoc tribunals for the former Yugoslavia and for Rwanda have determined that three conditions must be met before a superior can be held responsible for the criminal acts of his subordinates: (1) the existence of a superior-subordinate relationship; (2) the superior knew or had reason to know that the subordinate was about to commit criminal acts or had done so; and (3) the superior failed to take necessary and reasonable measures to prevent such acts, or to punish the offenders thereof. The first condition, the existence of a superior-subordinate relationship, requires that a hierarchical relationship between superior and subordinate exist, which may be demonstrated to exist (or to have existed) by virtue of an accused party's de facto or de jure position of superiority. What must be demonstrated is that the superior had "effective control" over the persons committing the alleged offenses, that is, that he had the material ability to prevent the offenses or to punish the offenders. Second, the superior must be shown to have known or have had reason to know that his or her subordinate was about to commit or had committed a crime. It must be proven that the superior had actual knowledge, established through either direct or circumstantial evidence, that subordinates were planning to commit or had committed crimes within the jurisdiction of the tribunal, or that he possessed information that would have at least put him on notice of the risk of such crimes—such information thereby alerting him to the need for additional investigation to determine whether crimes were about to be committed or had been committed by the subordinates. Third, it must be established that the superior failed to take necessary and reasonable measures to prevent or punish the crimes of his subordinates. The measures required of the superior are limited to those that are feasible in the relevant circumstances and are "within his or her power" to enact. A superior is not obliged to perform "the impossible," but he has a duty to exercise the powers he does have within the confines of these limitations.

A commander would almost be in a position to prevent the development of genocidal intent on the part of his subordinates, nor should the law expect him to do so. What the individual of superior rank is required to do, however, is to prevent acts such as killing and the inflicting of serious physical harm when he knew or had reason to know that these acts were about to be committed, or to punish the acts when they had already taken place. The measures (to prevent or punish) that the superior is obligated to enact are dictated, in part, by the nature of the crimes committed or about to be committed by subordinates. Because of the seriousness of the offenses that may constitute genocide, a superior is obligated to implement those measures to prevent or punish with some urgency.

The chief difficulty that attaches to the criminal liability of a commanding officer when applied to genocide (as with complicity in genocide) relates to the mental state that the commanding officer must be shown to possess or to have possessed in order that he be held responsible for the acts of subordinates. Although knowledge of the relevant acts (as defined above) is sufficient, in principle, for a superior to be held responsible for the acts of his subordinates, the crime of genocide must take in a specific intent to destroy in whole or in part a group as such. How can these two standards be reconciled? Is it sufficient for a commanding officer to know or to have had reason to know that his subordinates were committing genocidal acts in order that he be held responsible for genocide, as a commanding officer? Or must the commander himself possess the intent to destroy the group in whole or in part? Existing case law on this point is inconsistent, and arguments have been advanced in support of both positions. As was found previously, it seems more appropriate to require that the commanding officer be shown to have possessed the genocidal intent himself. The fact that a commander may have known of his subordinates' genocidal mens rea has evidential relevance to the extent that it may serve to establish his own genocidal mindset, but it is not in itself sufficient to establish his responsibility, as commander, for genocidal activities.

Joint Criminal Enterprise and Genocide

Joint criminal enterprise or common purpose doctrine is a concept that international law has borrowed from common law. Because this form of liability has the potential to lead to the excessive criminalization of behaviors and has created some legitimate concerns from the perspective of defendants, it has become a very contentious issue indeed.

Three forms of joint criminal enterprise have been recognized under customary international law. One is the instance in which all participants share the same criminal intent. The second is essentially similar to the first in that it too requires the shared intent of participants, but is limited, for all intends and purposes, to cases that involve criminal actions that took place in concentration camps. The third relates to the situation in which all participants share a common intention to carry out particular criminal acts, but in which one of the participants commits an act that falls outside of the intended joint criminal enterprise. If the act were nevertheless a "natural and foreseeable consequence" of the carrying out of the agreed joint criminal enterprise, all participants incur criminal liability for that act.

Joint criminal enterprise liability is different from membership in a criminal organization, which was criminalized as a separate offense in the Nuremberg Trials, and in subsequent trials that came under the sway of Control Council Law No. 10 (where it was determined that knowing and voluntary membership in one such organization was sufficient to entail criminal responsibility). Criminal liability pursuant to a joint criminal enterprise is not a liability for mere membership in an organization or for conspiring to commit crimes, but a form of liability concerned with participation in the commission of a crime as part of a joint criminal enterprise—a different matter.

Joint criminal enterprise is also different from the crime of "conspiracy." Although a judgment of conspiracy requires a showing that several individuals agreed to commit a crime or a number of crimes, proof of a joint criminal enterprise requires, in addition to such a showing, that the parties to an agreement took action in the furtherance of that agreement. For all three forms of joint criminal enterprise, the prosecution must establish the existence of that criminal enterprise and the part therein of the accused. A joint criminal enterprise may be said to exist where there is an understanding or arrangement amounting to an agreement between two or more individuals that they will commit a criminal offense. A person may participate in such a joint criminal enterprise in any of the following ways: (1) by participating directly in the commission of the agreed upon crime itself (as a principal offender); (2) by being a part of the criminal proceedings at the time the crime is committed, and (with knowledge that the crime is being committed or is to be committed) by intentionally assisting or encouraging another participant in the joint criminal enterprise to commit that crime; or (3) by acting in the furtherance of a particular scheme according to which the crime is committed (as evidenced by the position of authority or function of the accused), and with knowledge of the nature of that scheme and intent to further that scheme. If the agreed upon crime is committed by one or other of the participants in that joint criminal enterprise, all of the participants in that enterprise are guilty of the crime, regardless of the part played by each in its commission.

As far as the element of mens rea is concerned, proof of the existence of the first and second types of joint criminal enterprise requires that the prosecution establish that each of the persons charged and (even if not one of those charged) the principal offender or offenders shared a common state of mind, which is required for the crime's being pursued. Concerning the third type of joint criminal enterprise, the prosecution must show that the accused possessed the intention to participate in and further the criminal activity or criminal purpose of a group and contributed to the joint criminal enterprise or at least to the commission of a crime by the group. Responsibility for a crime or crimes that had not been agreed upon would be incurred by an accused person only when it was foreseeable that such a crime or crimes might be perpetrated by one or more members of the group and the accused willingly embraced the risk that would inevitably attach to a crime's being committed. What then is the mens rea that must be shown to have existed for an individual charged for his or her part in a joint criminal enterprise, the purpose of which was to commit genocide or a genocide-related offense? Would the participant's knowledge of the fact that such a crime or crimes were being envisioned by others be sufficient to establish his or her guilt, or would the participant have to have shared the genocidal intent of the principal offender? In parallel with what has been argued above in relation to "complicity" and "command responsibility," it seems that the most logical, and most sensible, conclusion would be that, regardless of the form of criminal participation, a finding of guilt for any sort of participation in a genocidal offense requires that the accused possess a genocidal intent. The matter, however, is not settled.

SEE ALSO Attempt; Bystanders; Conspiracy; Incitement; Superior (or Command) Responsibility


Cassese, A. (2002). "Genocide." In The Rome Statute of the International Criminal Court: A Commentary, ed. A. Cassese, P. Gaeta, and J. R. W. D. Jones. Oxford: Oxford University Press.

Schabas, William A. (2000). Genocide in International Law. Cambridge, U.K.: Cambridge University Press.

Guénaël Mettraux

I am setting forth the above in my personal capacity. This article represents neither the policies of the Office of the Prosecutor of the International Criminal Tribunal for the Former Yugoslavia nor the United Nations.

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