A/HRC/8/16 page 11 35. As mentioned above, international criminal law prohibits aiding and abetting international crimes. Aiding and abetting requires (i) an act or omission having a substantial effect on the commission of an international crime and (ii) knowledge of contributing to the crime.18 (a) Act or omission that has a substantial effect 36. Cases on aiding and abetting heard in ad hoc international tribunals have found that aiding and abetting consists of “acts [by individuals] directed to assist, encourage or lend moral support to the perpetration of a crime, and which have a substantial effect upon its perpetration”.19 37. The assistance need not cause, or be a necessary contribution to, the commission of the crime. In other words, it does not have to be shown that the crime would not have happened without the contribution. Furthermore, the assistance may occur before, during, or after the principal crime has been committed, and it need not occur within geographic proximity to the crime.20 38. The International Law Commission Code indicates that an accomplice must provide the kind of assistance that contributes “directly and substantially” to the commission of the crime. A substantial and direct contribution could be, for example, providing the means that enable the perpetrator to commit the crime. The assistance must facilitate the crime in some significant way.21 18 The Statutes for the ICC, ICTY and ICTR as well as other international criminal tribunals provide for individual liability based on aiding and abetting. In the jurisprudence before the ICTY and ICTR, the tribunals have emphasized that such liability will depend on proving a physical element (substantial assistance) and a mental element (knowledge). For example, see Furundžija (ICTY Trial Chamber), 10 December 1998, para. 249; Simić (ICTY Appeals Chamber), 28 November 2006, paras. 85-86; Blagojevic and Jokic (ICTY Appeals Chamber), 9 May 2007, para. 127; and Ntagerura (ICTR Appeals Chamber), 7 July 2006, para. 370. 19 For example, see Simić (ICTY Appeals Chamber), 28 November 2006, para. 85; Blagojevic and Jokic (ICTY Appeals Chamber), 9 May 2007, para. 127; Blaskic (ICTY Appeals Chamber), 29 July 2005, paras. 45-46; Vasiljevic (ICTY Appeals Chamber), 25 February 2004, para. 102; and Ntagerura (ICTR Appeals Chamber), 7 July 2006, para. 370. 20 Blaskic (ICTY Appeals Chamber), 29 July 2004, para. 48. Also see Blagojevic and Jokic (ICTY Appeals Chamber), 9 May 2007, para. 127; Simić (ICTY Appeals Chamber), 28 November 2006, para. 85; and Ntagerura (ICTR Appeals Chamber), 7 July 2006, para. 372. 21 According to the International Law Commission, this standard is consistent with the other relevant international provisions including the Nuremberg Charter and the ICTY and ICTR Statutes. See Yearbook of the International Law Commission, 1996, vol. II, Part Two, document A/51/10, p. 21, para. (11) of the commentary to article 1.