Regarding aiding and betting by tacit approval and encouragement, the Appeals Chamber held:

273. […] An accused can be convicted for aiding and abetting a crime when it is established that his conduct amounted to tacit approval and encouragement of the crime and that such conduct substantially contributed to the crime.[1] This form of aiding and abetting is not, strictly speaking, criminal responsibility for omission.[2] […] The Trial Chamber in Kayishema and Ruzindana held that “individual responsibility pursuant to Article 6(1) [that is, individual criminal responsibility under 7(1) of the Tribunal’s Statute] is based, in this instance, not on a duty to act, but from the encouragement and support that might be afforded to the principals of the crime from such an omission.”[3] In such cases the combination of a position of authority and physical presence on the crime scene allowed the inference that non-interference by the accused actually amounted to tacit approval and encouragement.[4]

45. In Vasiljević, the Appeals Chamber set out the actus reus and mens rea of aiding and abetting. It stated:

(i) The aider and abettor carries out acts specifically directed to assist, encourage or lend moral support to the perpetration of a certain specific crime (murder, extermination, rape, torture, wanton destruction of civilian property, etc.), and this support has a substantial effect upon the perpetration of the crime. […]

(ii) In the case of aiding and abetting, the requisite mental element is knowledge that the acts performed by the aider and abettor assist [in] the commission of the specific crime of the principal. […][1]

The Appeals Chamber considers that there are no reasons to depart from this definition.

46. In this case, the Trial Chamber, following the standard set out in Furundžija, held that the actus reus of aiding and abetting “consists of practical assistance, encouragement, or moral support which has a substantial effect on the perpetration of the crime.”[2] It further stated that the mens rea required is “the knowledge that these acts assist the commission of the offense.”[3] The Appeals Chamber considers that the Trial Chamber was correct in so holding.

47. The Trial Chamber further stated that the actus reus of aiding and abetting may be perpetrated through an omission, “provided this failure to act had a decisive effect on the commission of the crime and that it was coupled with the requisite mens rea.”[4]  It considered:

In this respect, the mere presence at the crime scene of a person with superior authority, such as a military commander, is a probative indication for determining whether that person encouraged or supported the perpetrators of the crime.[5]

The Appeals Chamber leaves open the possibility that in the circumstances of a given case, an omission may constitute the actus reus of aiding and abetting. 

48. The Trial Chamber in this case went on to state:

Proof that the conduct of the aider and abettor had a causal effect on the act of the principal perpetrator is not required. Furthermore, participation may occur before, during or after the act is committed and be geographically separated therefrom.[6]

The Appeals Chamber reiterates that one of the requirements of the actus reus of aiding and abetting is that the support of the aider and abettor has a substantial effect upon the perpetration of the crime.  In this regard, it agrees with the Trial Chamber that proof of a cause-effect relationship between the conduct of the aider and abettor and the commission of the crime, or proof that such conduct served as a condition precedent to the commission of the crime, is not required.  It further agrees that the actus reus of aiding and abetting a crime may occur before, during, or after the principal crime has been perpetrated, and that the location at which the actus reus takes place may be removed from the location of the principal crime.

49. In relation to the mens rea of an aider and abettor, the Trial Chamber held that “in addition to knowledge that his acts assist the commission of the crime, the aider and abettor needs to have intended to provide assistance, or as a minimum, accepted that such assistance would be a possible and foreseeable consequence of his conduct.”[7] However, as previously stated in the Vasiljević Appeal Judgement, knowledge on the part of the aider and abettor that his acts assist in the commission of the principal perpetrator’s crime suffices for the mens rea requirement of this mode of participation.[8] In this respect, the Trial Chamber erred.

50. The Trial Chamber agreed with the statement in the Furundžija Trial Judgement that “it is not necessary that the aider and abettor…know the precise crime that was intended and which in the event was committed. If he is aware that one of a number of crimes will probably be committed, and one of those crimes is in fact committed, he has intended to facilitate the commission of that crime, and is guilty as an aider and abettor.”[9] The Appeals Chamber concurs with this conclusion.

127. […] The requisite mental element of aiding and abetting is knowledge that the acts performed assist the commission of the specific crime of the principal perpetrator.[1] In cases of specific intent crimes such as persecutions or genocide, the aider and abettor must know of the principal perpetrator’s specific intent.[2]

221.  In describing the applicable law for aiding and abetting, the Trial Chamber restated the formulation of the mens rea for aiding and abetting found in the Vasiljević Appeal Judgement:

[I]t is not required that the aider and abettor shared the mens rea required for the crime; it is sufficient that the aider and abettor had knowledge that his or her own acts assisted in the commission of the specific crime by the principal offender. The aider and abettor must also be aware of the “essential elements” of the crime committed by the principal offender, including the state of mind of the principal offender.[3]

The Appeals Chamber has applied this formulation consistently in its judgements.[4] Consequently, the Appeals Chamber finds no legal error on the part of the Trial Chamber in this regard.

1812. […] [T]he criminal responsibility of an aider and abettor does not require the contribution to the crime of persecution to go to the discriminatory nature of this crime […][1]

43. The Prosecution submits that the Trial Chamber found Atif Krdžić responsible for aiding and abetting by omission.[1] The Appeals Chamber recalls that omission proper may lead to individual criminal responsibility under Article 7(1) of the Statute where there is a legal duty to act.[2] The Appeals Chamber has never set out the requirements for a conviction for omission in detail.[3] However, at a minimum, the offender’s conduct would have to meet the basic elements of aiding and abetting. Thus, his omission must be directed to assist, encourage or lend moral support to the perpetration of a crime and have a substantial effect upon the perpetration of the crime (actus reus).[4] The aider and abettor must know that his omission assists in the commission of the crime of the principal perpetrator[5] and must be aware of the essential elements of the crime which was ultimately committed by the principal (mens rea).[6]

321. The actus reus of aiding and abetting is constituted by acts or omissions that assist, further, or lend moral support to the perpetration of a specific crime, and which substantially contribute to the perpetration of the crime.[1] The mens rea for aiding and abetting is knowledge that acts performed by the aider and abettor assist in the commission of the crime by the principal.[2] It is well established that it is not necessary for an accused to know the precise crime which was intended and which in the event was committed, but he must be aware of its essential elements.[3] If an accused is aware that one of a number of crimes will probably be committed, and one of those crimes is in fact committed, he has intended to facilitate the commission of that crime.[4]

51.     The Appeals Chamber draws attention to the distinction between the mental element required for aiding and abetting and that required for co-perpetration. In the case of aiding and abetting, the requisite mental element is knowledge that the acts committed by the aider and abettor further the perpetration of a specific crime by the principal offender. In the case of co-perpetration, the intent to perpetrate the crime or to pursue the joint criminal purpose must be shown.[1] The Appeals Chamber also recalls that in the Aleksovski Appeals Judgement it followed the Furundžija Judgement and held that “it is not necessary to show that the aider and abettor shared the mens rea of the principal, but it must be shown that […] the aider and abettor was aware of the essential elements of the crime which was ultimately committed by the principal.”[2] The Appeals Chamber also stated that “the aider and abettor [must be aware] of the essential elements of the crime committed by the principal (including his relevant mens rea).” The Appeals Chamber notes that no cogent reason was given which would justify this case-law being amended.[3]

52.     The Appeals Chamber considers that the aider and abettor in persecution, an offence with a specific intent, must be aware not only of the crime whose perpetration he is facilitating but also of the discriminatory intent of the perpetrators of that crime. He need not share the intent but he must be aware of the discriminatory context in which the crime is to be committed and know that his support or encouragement has a substantial effect on its perpetration. […]

89. The Appeals Chamber notes that in the Vasiljević Appeal Judgement, the Appeals Chamber discussed the correct distinction between co-perpetration by means of a joint criminal enterprise and aiding and abetting:

(i) The aider and abettor carries out acts specifically directed to assist, encourage or lend moral support to the perpetration of a certain specific crime (murder, extermination, rape, torture, wanton destruction of civilian property, etc.), and this support has a substantial effect upon the perpetration of the crime. By contrast, it is sufficient for a participant in a joint criminal enterprise to perform acts that in some way are directed to the furtherance of the common design.

(ii) In the case of aiding and abetting, the requisite mental element is knowledge that the acts performed by the aider and abettor assist the commission of the specific crime of the principal. By contrast, in the case of participation in a joint criminal enterprise, i.e. as a co-perpetrator, the requisite mens rea is intent to pursue a common purpose.[1]

90. Applying the Vasiljević definition, the Appeals Chamber considers that whether an aider and abettor is held responsible for assisting an individual crime committed by a single perpetrator or for assisting in all the crimes committed by the plurality of persons involved in a joint criminal enterprise depends on the effect of the assistance and on the knowledge of the accused. The requirement that an aider and abettor must make a substantial contribution to the crime in order to be held responsible applies whether the accused is assisting in a crime committed by an individual or in crimes committed by a plurality of persons. Furthermore, the requisite mental element applies equally to aiding and abetting a crime committed by an individual or a plurality of persons. Where the aider and abettor only knows that his assistance is helping a single person to commit a single crime, he is only liable for aiding and abetting that crime. This is so even if the principal perpetrator is part of a joint criminal enterprise involving the commission of further crimes. Where, however, the accused knows that his assistance is supporting the crimes of a group of persons involved in a joint criminal enterprise and shares that intent, then he may be found criminally responsible for the crimes committed in furtherance of that common purpose as a co-perpetrator.

91. The Appeals Chamber emphasizes that joint criminal enterprise is simply a means of committing a crime; it is not a crime in itself.[2] Therefore, it would be inaccurate to refer to aiding and abetting a joint criminal enterprise. The aider and abettor assists the principal perpetrator or perpetrators in committing the crime.

92. The Appeals Chamber notes that the distinction between these two forms of participation is important, both to accurately describe the crime and to fix an appropriate sentence. Aiding and abetting generally involves a lesser degree of individual criminal responsibility than co-perpetration in a joint criminal enterprise.[3]

86. The Appeals Chamber has explained that an “aider and abettor commit[s]] acts specifically aimed at assisting, encouraging, or lending moral support for the perpetration of a specific crime, and that this support ha[s] a substantial effect on the perpetration of the crime.”[1] Whether a particular contribution qualifies as “substantial” is a “fact-based inquiry”; such assistance need not “serve as condition precedent for the commission of the crime.”[2] With regard to the mens rea required for aiding and abetting, the Appeals Chamber has held that “[t]]he requisite mental element [...]] is knowledge that the acts performed assist the commission of the specific crime of the principal perpetrator.”[3] Specific intent crimes such as genocide require that “the aider and abettor must know of the principal perpetrator’s specific intent.”[4]

87. Kalimanzira’s contention that the Trial Chamber erred in finding that he made a substantial contribution to the killings at Kabuye hill is not convincing. The Trial Chamber reasonably concluded that he substantially contributed to the massacre by encouraging Tutsis to seek refuge at Kabuye hill and by providing armed reinforcements to those trying to kill the Tutsis there. Kalimanzira’s assertion that he did not substantially aid the assault on Kabuye hill rests on his claim that no credible witnesses who were also principal perpetrators placed him there.[5] However, this claim does not take into account the evidence provided by Tutsi survivors of the attacks. It was on the basis of their testimonies that the Trial Chamber placed him at Kabuye hill on 23 April 1994.[6] The Appeals Chamber recalls that it is not necessary for a principal perpetrator to be aware of the aider and abettor’s contribution.[7] It further recalls the Trial Chamber’s finding that the attacks at Kabuye hill involved a large number of individuals over a broad terrain and long period of time.[8] In this context, it was reasonable for the Trial Chamber to conclude that Kalimanzira provided substantial assistance to the massacre at Kabuye hill even if this assistance was not known to principal perpetrators who testified before it.[9]

425. The Appeals Chamber notes that the physical presence of an aider and abettor at or near the scene of the crime may be a relevant factor in cases of aiding and abetting by tacit approval.[1] Further, the actus reus of aiding and abetting may be fulfilled remotely.[2] It is also well established that the actus reus of aiding and abetting may be fulfilled before, during, or after the principal crime has been perpetrated.[3] Thus, Sredoje Lukić’s submission that the Trial Chamber erroneously construed the actus reus of aiding and abetting is dismissed.

428. It is well established that the mens rea of aiding and abetting requires that an aider and abettor know that his acts would assist in the commission of the crime by the principal perpetrator and must be aware of the “essential elements” of the crime.[1] It does not require that he shares the intention of the principal perpetrator of such crime, as Sredoje Lukić submits. […]

440. The Appeals Chamber further recalls that an aider and abettor must know that his acts would assist the commission of the crime by the principal perpetrators and must be aware of the “essential elements” of the crime committed by the principal perpetrator.[2] […]

458. The Trial Chamber’s statement of the law with regard to the mens rea of aiding and abetting is correct.[3] The special intent crime of persecutions requires in addition that:

[the aider and abettor] be aware not only of the crime whose perpetration he is facilitating but also of the discriminatory intent of the perpetrators of that crime. He need not share the intent but he must be aware of the discriminatory context in which the crime is to be committed and know that his support or encouragement has a substantial effect on its perpetration.[4]

162. [...] The Trial Chamber [in the Furundžija Appeal Judgement] had earlier stated the conclusion that it is not necessary to show that the aider and abettor shared the mens rea of the principal, but it must be shown that the aider and abettor was aware of the relevant mens rea on the part of the principal.[1]  It is clear that what must be shown is that the aider and abettor was aware of the essential elements of the crime which was ultimately committed by the principal.

58. The Appeals Chamber considers it firmly established that, to satisfy the mens rea requirement for aiding and abetting, “[i]t must be shown that the aider and abettor knew that his own acts assisted the commission of that specific crime by the principal” (for example, murder, extermination, rape, torture)[1] and that the aider and abettor was “aware of the essential elements of the crime which was ultimately committed by the principal”.[2] Where the mens rea of the principal perpetrator is an element of the principal crime, the aider and abettor need not share the intent of the principal perpetrator,[3] but he or she must be aware of the intent of the principal perpetrator.[4] Mens rea can be established if the aider and abettor is not certain which of a number of crimes will ultimately be committed.[5] In this regard, where an accused “is aware that one of a number of crimes will probably be committed, and one of those crimes is in fact committed, he has intended to facilitate the commission of that crime, and is guilty as an aider and abettor.”[6] Accordingly, the Trial Chamber correctly set out the legal standard for the mens rea of aiding and abetting.[7]

Judge Patrick Robinson appended a Partially Dissenting Opinion to the Appeals Judgement on the issue of the Trial Chamber’s discretion and the assessment of a fair and expeditious trial.

134. The Appeals Chamber recalls that while individual criminal responsibility generally requires the commission of a positive act, this is not an absolute requirement.[1] In particular, the Appeals Chamber has previously found that “the omission to act where there is a legal duty to act can lead to individual criminal responsibility under Article 7(1) of the Statute”.[2] Moreover, the Appeals Chamber has consistently found that, in the circumstances of a given case, the actus reus of aiding and abetting may be perpetrated through an omission.[3]

135. Accordingly, the Appeals Chamber finds that the Trial Chamber properly considered aiding and abetting by omission as a recognised mode of liability under the International Tribunal’s jurisdiction.[4]

151. The Appeals Chamber recalls that it has previously recognised that the breach of a duty to act imposed by the laws and customs of war gives rise to individual criminal responsibility.[1] The Appeals Chamber further recalls that Šljivančanin’s duty to protect the prisoners of war was imposed by the laws and customs of war.[2] Thus, the Appeals Chamber considers that Šljivančanin’s breach of such duty gives rise to his individual criminal responsibility. Therefore, it is not necessary for the Appeals Chamber to further address whether the duty to act, which forms part of the basis of aiding and abetting by omission, must stem from a rule of criminal law.

93. [T]he Appeals Chamber considers that even though Šljivančanin no longer had de jure authority over the military police deployed at Ovčara, had he ordered the military police not to withdraw, these troops may well have, in effect, obeyed his order to remain there, considering he had been originally vested with the authority for the entire evacuation of the Vukovar Hospital and entrusted with responsibility for protecting the prisoners of war. In particular, Šljivančanin could have informed the military police deployed at Ovčara that Mrkšić’s order was in breach of the overriding obligation under the laws and customs of war to protect the prisoners of war, and thus constituted an illegal order.

94. Indeed, issuing an order contrary to Mrkšić’s to the military police of the 80 mtbr was a course of action that would have required Šljivančanin to go beyond the scope of his de jure authority, which had been effectively removed by virtue of Mrkšić withdrawal order.[1] Nonetheless, the illegality of Mrkšić’s order required [ljivančanin to do so. To further support this conclusion, the Appeals Chamber recalls the analysis in the Čelebići Trial Judgement which implies that in the context of preventing the commission of a war crime, an officer may be expected to act beyond the strict confines of his de jure authority:

Likewise, the finding in the High Command case that a commander may be held criminally liable for failing to prevent the execution of an illegal order issued by his superiors, which has been passed down to his subordinates independent of him, indicates that legal authority to direct the actions of subordinates is not seen as an absolute requirement for the imposition of command responsibility. Similarly, the finding in the Toyoda case, whereby the tribunal rejected the alleged importance of what it called the "theoretical" division between operational and administrative authority, may be seen as supporting the view that commanders are under an obligation to take action to prevent the commission of war crimes by troops under their control despite a lack of formal authority to do so. An officer with only operational and not administrative authority does not have formal authority to take administrative action to uphold discipline, yet in the view of the tribunal in the Toyoda case; "[t]he responsibility for discipline in the situation facing the battle commander cannot, in the view of practical military men, be placed in any hands other than his own.”[2]

Although the Trial Chamber in Čelebići discussed this in the context of superior responsibility, the Appeals Chamber considers that the principle that an officer may be required, within the limits of his capacity to act, to go beyond his de jure authority to counteract an illegal order is equally applicable to the present case.

See also footnote 331:

It is a principle of international humanitarian law that subordinates are bound not to obey manifestly illegal orders or orders that they knew were illegal. See Hostage Case (United States v. Wilhelm List et al., Trials of War Criminals, Vol. XI, p. 1236): “[T]he general rule is that members of the armed forces are bound to obey only the lawful orders of their commanding officers and they cannot escape criminal liability by obeying a command which violates international law and outrages fundamental concepts of justice”. See also Erdemović 1996 Sentencing Judgement, para. 18 (“Although the accused did not challenge the manifestly illegal order he was allegedly given, the Trial Chamber would point out that according to the case-law referred to, in such an instance, the duty was to disobey rather than to obey.”), fn. 12 (“Trial of Rear-Admiral Nisuke Masuda and four others of the Imperial Japanese Navy, Jaluit Atoll Case, U.S. Military Commission, U.S. Naval Air Base, Kwajalein Island, Kwajalein Atoll, Marshall Islands, 7-13 December 1945, Case No. 6, L.R.T.W.C., Vol. I, pp. 74-76, pp. 79-80. See also Trial of Wilhelm List and Others, U.S. Military Tribunal, Nuremberg, 8 July 1947-19 February 1948, L.R.T.W.C., Case No. 47, Vol. VIII, pp. 50-52 […].); Mrđa Sentencing Judgement, para. 67 (“As to the related issue of superior orders, Article 7(4) of the Statute states that ‛[t]he fact that an accused person acted pursuant to an order of a government or of a superior […] may be considered in mitigation of punishment if the Tribunal determines that justice so requires.’ […] [T]he orders were so manifestly unlawful that Darko Mrđa must have been well aware that they violated the most elementary laws of war and the basic dictates of humanity. The fact that he obeyed such orders, as opposed to acting on his own initiative, does not merit mitigation of punishment.”).

49. At the outset, the Appeals Chamber recalls that to enter a conviction for aiding and abetting murder by omission, at a minimum, all the basic elements of aiding and abetting must be fulfilled.[1] In this regard, the Appeals Chamber in Orić recalled that “omission proper may lead to individual criminal responsibility under Article 7(1) of the Statute where there is a legal duty to act”.[2] The actus reus of aiding and abetting by omission will thus be fulfilled when it is established that the failure to discharge a legal duty assisted, encouraged or lent moral support to the perpetration of the crime and had a substantial effect on the realisation of that crime.[3] The Appeals Chamber recalls that aiding and abetting by omission implicitly requires that the accused had the ability to act, such that there were means available to the accused to fulfil his duty.[4] Meanwhile, the required mens rea for aiding and abetting by omission is that “[t]he aider and abettor must know that his omission assists in the commission of the crime of the principal perpetrator and must be aware of the essential elements of the crime which was ultimately committed by the principal”.[5] As the Appeals Chamber held in the  Simić case,

it is not necessary that the aider and abettor knows either the precise crime that was intended or the one that was, in the event, committed. If he is aware that one of a number of crimes will probably be committed, and one of those crimes is in fact committed, he has intended to facilitate the commission of that crime, and is guilty as an aider and abetter.[6]

[…].

146. As Šljivančanin argues,[7] the Appeals Chamber has never set out the elements for a conviction for omission in detail.[8] In the Orić case, the Appeals Chamber considered the Trial Chamber’s findings in order to determine whether Atif Krdžić, Naser Orić’s subordinate, had been found responsible for aiding and abetting by omission.[9] It concluded that no such finding had been entered as the issue of whether Naser Orić’s subordinate had incurred criminal responsibility had not been resolved by the Trial Chamber.[10] In this context, with regard to the mode of liability of aiding and abetting by omission, the Appeals Chamber held that:

at a minimum, the offender’s conduct would have to meet the basic elements of aiding and abetting. Thus, his omission must be directed to assist, encourage or lend moral support to the perpetration of a crime and have a substantial effect upon the perpetration of the crime (actus reus). The aider and abettor must know that his omission assists in the commission of the crime of the principal perpetrator and must be aware of the essential elements of the crime which was ultimately committed by the principal (mens rea).[11]

Accordingly, the Appeals Chamber in Orić acknowledged that the basic elements of aiding and abetting apply notwithstanding whether this form of liability is charged as “omission”. The mens rea and actus reus requirements for aiding and abetting by omission are the same as for aiding and abetting by a positive act.[12] The critical issue to be determined is whether, on the particular facts of a given case, it is established that the failure to discharge a legal duty assisted, encouraged or lent moral support to the perpetration of the crime, and had a substantial effect on it. In particular, the question as to whether an omission constitutes “substantial assistance” to the perpetration of a crime requires a fact based enquiry.[13]

In footnote 526, the Appeals Chamber noted that:

The Appeals Chamber recalls that “the threshold for finding a “significant contribution” to a [joint criminal enterprise] is lower than the “substantial contribution” required to enter a conviction for aiding and abetting.” See Gotovina and Markač Appeal Judgement, para. 149. […]

500. The ICTY Appeals Chamber has explained, on several occasions, that an individual who aids and abets other individuals committing a specific intent offence may be held responsible if he assists the commission of the crime knowing the intent behind the crime.[1] More recently, as the Prosecution argued at the Appeal hearing, in the Krstić case the ICTY Appeals Chamber considered that the same principle applies to the Statute’s prohibition of genocide and that “[t]he conviction for aiding and abetting genocide upon proof that the defendant knew about the principal perpetrator’s genocidal intent is permitted by the Statute and case-law of the Tribunal.”[2] In reaching this conclusion, the Krstić Appeals Chamber derived aiding and abetting as a mode of liability from Article 7(1) of the ICTY Statute, but also considered that aiding and abetting constitutes a form of complicity, suggesting that complicity under Article 2 of the ICTR Statute and Article 4 of the ICTY Statute would also encompass aiding and abetting, based on the same mens rea, while other forms of complicity may require proof of specific intent.

501. The Appeals Chamber endorses this view and finds that a conviction for aiding and abetting genocide upon proof that the defendant knew about the principal perpetrator’s genocidal intent is permitted by the Statute and case-law of this Tribunal. […]

52. The Appeals Chamber has explained that an “aider and abettor commit[s]] acts specifically aimed at assisting, encouraging, or lending moral support for the perpetration of a specific crime, and that this support had a substantial effect on the perpetration of the crime.”[1] It recalls that there is no requirement of a cause-effect relationship between the conduct of the aider and abettor and the commission of the crime nor that such conduct served as a condition precedent to the commission of the crime.[2] It is sufficient for the aider and abettor’s assistance or encouragement to have had a substantial effect on the realisation of that crime,[3] the establishment of which is a “fact-based inquiry”.[4] […]

1772. It is firmly established in the jurisprudence of the Tribunal that to satisfy the mens rea requirement for aiding and abetting, it must be shown that the aider and abettor knew that his acts or omissions assisted the commission of the specific crime by the principal, and that the aider and abettor was aware of the essential elements of the crime which was ultimately committed, including the intent of the principal perpetrator.[1] In addition, the Appeals Chamber recalls that it is not necessary that the aider and abettor know the precise crime that was intended and was in fact committed – if he is aware that one of a number of crimes will probably be committed, and one of those crimes is committed, he has intended to facilitate the commission of that crime, and is guilty as an aider and abettor.[2]

1773. The Appeals Chamber has previously defined “specific crime” as referring to, for example, “murder, extermination, rape, torture, wanton destruction of civilian property, etc.”[3] There is no legal requirement that the aider and abettor know every detail of the crime that was eventually committed. Nonetheless, the degree of knowledge pertaining to the details of the crime required to satisfy the mens rea of aiding and abetting will depend on the circumstances of the case, including the scale of the crimes and the type of assistance provided.

The Appeals Chamber examined the issue of "specific direction", namely whether a chamber must determine whether the accused's alleged acts and omissions were specifically directed to assist the commission of the concerned crimes.

1622.  The Appeals Chamber recalls that where it is faced with previous decisions that are conflicting, it is obliged to determine which decision it will follow, or whether to depart from both decisions for cogent reasons in the interests of justice.[1] In view of the divergence between the Mrkšić and Šljivančanin and Lukić and Lukić Appeal Judgements, on one hand, and the Perišić Appeal Judgement, on the other hand, [with regard to the issue of whether “specific direction” is an element of the actus reus of aiding and abetting liability] the Appeals Chamber, Judge Tuzmukhamedov dissenting, will determine the correct approach.[2] In so doing, mindful of its duty to act in the interests of legal certainty and predictability while ensuring that justice is done in all cases,[3] the Appeals Chamber will consider the jurisprudence of the Tribunal and the ICTR as well as customary international law to ascertain where the law stands on the issue of specific direction.

[…]

1649.  Based on the foregoing, the Appeals Chamber, Judge Tuzmukhamedov dissenting, comes to the compelling conclusion that “specific direction” is not an element of aiding and abetting liability under customary international law. Rather, as correctly stated in the Furundžija Trial Judgement and confirmed by the Blaškić Appeal Judgement, under customary international law, the actus reus of aiding and abetting “consists of practical assistance, encouragement, or moral support which has a substantial effect on the perpetration of the crime.”[4] The required mens rea is “the knowledge that these acts assist the commission of the offense”.[5] The Appeals Chamber reaffirms the position taken by the Blaškić Appeal Judgement in this regard.

1650.  Accordingly, the Appeals Chamber confirms that the Mrkšić and Šljivančanin and Lukić and Lukić Appeal Judgements stated the prevailing law in holding that “‘specific direction’ is not an essential ingredient of the actus reus of aiding and abetting”,[6] accurately reflecting customary international law and the legal standard that has been constantly and consistently applied in determining aiding and abetting liability.[7] Consequently, the Appeals Chamber, Judge Tuzmukhamedov dissenting, unequivocally rejects the approach adopted in the Perišić Appeal Judgement as it is in direct and material conflict with the prevailing jurisprudence on the actus reus of aiding and abetting liability and with customary international law in this regard.[8]

See also paras 1618-1621, 1623-1648, in which the Appeals Chamber examined the jurisprudence of the Tribunal and the ICTR as well as customary international law.

102.  Participation in a joint criminal enterprise is a form of “commission” under Article 7(1) of the Statute.  The participant therein is liable as a co-perpetrator of the crime(s).  Aiding and abetting the commission of a crime is usually considered to incur a lesser degree of individual criminal responsibility than committing a crime.  In the context of a crime committed by several co-perpetrators in a joint criminal enterprise, the aider and abettor is always an accessory to these co-perpetrators, although the co-perpetrators may not even know of the aider and abettor’s contribution.  Differences exist in relation to the actus reus as well as to the mens rea requirements between both forms of individual criminal responsibility:

(i) The aider and abettor carries out acts specifically directed to assist, encourage or lend moral support to the perpetration of a certain specific crime (murder, extermination, rape, torture, wanton destruction of civilian property, etc.), and this support has a substantial effect upon the perpetration of the crime.  By contrast, it is sufficient for a participant in a joint criminal enterprise to perform acts that in some way are directed to the furtherance of the common design.

(ii) In the case of aiding and abetting, the requisite mental element is knowledge that the acts performed by the aider and abettor assist the commission of the specific crime of the principal.  By contrast, in the case of participation in a joint criminal enterprise, i.e. as a co-perpetrator, the requisite mens rea is intent to pursue a common purpose.

214. The Appeals Chamber recalls that the actus reus of aiding and abetting is constituted by acts or omissions specifically aimed at assisting, encouraging, or lending moral support to the perpetration of a specific crime, and which have a substantial effect upon the perpetration of the crime.[1] Whether a particular contribution qualifies as “substantial” is a “fact-based inquiry”, and need not “serve as condition precedent for the commission of the crime.”[2]

[…]

216. The Appeals Chamber considers that it was reasonable for the Trial Chamber to conclude that Ntawukulilyayo substantially contributed to the Kabuye hill killings by encouraging Tutsis to seek refuge there and then providing reinforcements to those attempting to kill them. These acts alone suffice to constitute the actus reus of aiding and abetting. […]

104. Turning to the question of specific direction, the Appeals Chamber recalls that, in the Šainović et al. Appeal Judgement, which was issued subsequent to the Perišić Appeal Judgement, it clarified that specific direction is not an element of aiding and abetting liability.[1] In arriving at this conclusion, it carefully reviewed the jurisprudence of the Tribunal and the ICTR in this regard[2] and re-examined the elements of aiding and abetting liability under customary international law.[3] The Appeals Chamber then observed that, neither in the jurisprudence of the Tribunal and the ICTR nor under customary international law, had specific direction been considered to be an element of aiding and abetting liability.[4] As a result, it rejected the approach adopted in the Perišić Appeal Judgement, which required specific direction as an element of the actus reus of aiding and abetting,[5] and held that this approach was “in direct and material conflict with the prevailing jurisprudence on the actus reus of aiding and abetting liability and with customary international law”.[6] The Appeals Chamber re-affirmed that, “under customary international law, the actus reus of aiding and abetting ‘consists of practical assistance, encouragement, or moral support which has a substantial effect on the perpetration of the crime’” and that “[t]he required mens rea is ‘the knowledge that these acts assist the commission of the offense’.”[7]

105. Subsequently, in the Popović et al. Appeal Judgement, the Appeals Chamber re-affirmed that “‘specific direction’ is not an element of aiding and abetting liability under customary international law”.[8]

106. Accordingly, the Appeals Chamber, Judge Agius and Judge Afanđe dissenting, finds that the Trial Chamber erred in law in requiring that the acts of the aider and abettor be specifically directed to assist the commission of a crime. This also means that the Trial Chamber erred in law in making a finding on a substantial effect of the contributory acts contingent upon establishing specific direction, by holding that, when assessing whether the acts carried out by the aider and abettor have a substantial effect on the perpetration of a crime, the Trial Chamber must find that they are specifically directed to assist that crime.[9]

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128. Finally, Judge Afanđe dissenting, if the new trial chamber were to examine the responsibility of Stanišić and Simatović for aiding and abetting the crimes, the Appeals Chamber, Judge Agius and Judge Afanđe dissenting, instructs it to apply the correct law on aiding and abetting liability as set out above, which does not require that the acts of the aider and abettor be specifically directed to assist the commission of a crime.[10] In this regard, the Appeals Chamber notes that the principle of lex mitior, as alleged by Simatović, is not applicable to the present case. Whereas this principle applies to situations where there is a change in the concerned applicable law,[11] as noted above, it has been established that specific direction has never been part of the elements of aiding and abetting liability under customary international law, which the Tribunal has to apply.[12] Accordingly, the Appeals Chamber dismisses Simatović’s argument in this respect.[13]

3345.            As an inchoate crime,[1] direct and public incitement to commit genocide is completed as soon as the discourse in question is uttered or published, even though the effects of incitement may extend in time,[2] and is punishable even if no act of genocide has resulted therefrom.[3] Accordingly, in order for Kanyabashi to be found responsible for aiding and abetting direct and public incitement to commit genocide, it would have to be established that he substantially contributed to Kambanda’s and Sindikubwabo’s inciting speeches themselves and not, as the Prosecution suggests, to the effects of their incitements by “reiterat[ing] and reinforc[ing] their message”.[4] The Appeals Chamber recalls that the Trial Chamber determined that Kanyabashi spoke after Kambanda and Sindikubabwo delivered their speeches.[5] The Prosecution points to no evidence or findings demonstrating that Kanyabashi’s conduct provided substantial assistance to Sindikubwabo or Kambanda in the commission of their direct and public incitement to commit genocide, either before, during, or after their respective speeches.