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]

149. With respect to aiding and abetting, the Appeals Chamber notes that the Trial Chamber did not explicitly find whether Markač made a “substantial contribution” to relevant crimes by the Special Police.[1] While the Trial Chamber concluded that the evidence it considered proved that Markač’s Failure to Act constituted a significant contribution to the JCE,[2] the Appeals Chamber has held that the threshold for finding a “significant contribution” to a JCE is lower than the “substantial contribution” required to enter a conviction for aiding and abetting.[3] Thus the Trial Chamber’s finding of a significant contribution is not equivalent to the substantial contribution required to enter a conviction for aiding and abetting.