The Appeals Chamber noted that, although cooperation with the Prosecution is the only mitigating factor referred to expressly in the Rules, “substantial cooperation” is not defined, and it is for the Trial Chamber to assess the extent and the nature of the accused’s cooperation. The Appeals Chamber considered that the assessment of whether or not the cooperation is “substantial” “primarily depends on the specific circumstances of each case and that substantial cooperation does not solely rest on one specific act of an accused but must be assessed as a whole”. The qualification of an accused’s cooperation as “substantial” will depend on the quantity and the quality of the information provided. See paragraph 51.

52. The Appeals Chamber stresses that the assessment of the quality of the provided information primarily depends on its “actual content”. In this regard, the provision of new information, “heard for the first time before this Tribunal”, has to be seen as particularly valuable. Special weight has previously also been given to the provision of unique and corroborative information to the Prosecution, as well as the identification of new crimes and perpetrators and of previously unknown mass graves. However, the content of the information is not the only criteria to be taken into account in the assessment of the quality of the information. Such quality […] will also depend on the earnestness of the accused in providing it.[2] […] Further, while the actual use by the Prosecution in other proceedings before the International Tribunal of information provided by an accused is not […] in itself proof of the quality of the submitted information, such use has to be seen […] as a significant indication of the value of this information.

On the earnestness of an accused’s cooperation, see also para. 63.

At para. 63, the Appeals Chamber also considered the determination within a plea agreement of any cooperation to be provided by an accused as significant indication of an accused’s willingness to cooperate with the Prosecution:

63. […] Although such specification is not mandatory, its inclusion is a significant indication of an accused’s willingness to cooperate with the Prosecution. It establishes clear obligations on the part of the accused, which can then be considered by a Trial Chamber when assessing the accused’s cooperation.