In light of the confidential nature of the use made of the information provided by the Appellant, the Appeals Chamber considered that, “where the Trial Chamber must evaluate an accused’s cooperation based on information solely in the possession of the Prosecution”, it must be established “whether the Trial Chamber has sufficiently assessed the evidence provided on an ex parte basis in order to protect the rights of the accused, where the accused himself does not have the opportunity to do so”. See para. 56.

The Appeals Chamber then detailed the practice to be followed by the Prosecution and the Trial Chambers in such cases:

57. […] the better practice is to first check whether the documents in question could be disclosed inter partes in order to allow the accused to himself comment on the Prosecution’s submissions.[1] This may in certain instances necessitate an application to another Chamber for a variation in protective measures. Where it is not possible for such documents to be submitted inter partes, it is within a Trial Chamber’s discretion to rely on the Prosecution’s ex parte assessment of the accused’s cooperation, as the Trial Chamber did in the instant case. In this event, the Appeals Chamber emphasises that the Prosecution must provide sufficient explanations in its assessment as to why it considers the information given by an accused valuable or not. The Trial Chamber should then evaluate the nature and extent of the accused’s cooperation and set out a reasoned opinion in writing.[2] Under the circumstances, such reasoned opinion is the Appellant’s only guide as to whether his right to a fair trial has been preserved.

61. […] The Appeals Chamber refers in this context to the approach taken in the Dragan Nikolić case, where the Trial Chamber requested the Prosecution at the Sentencing Hearing to provide documents that “would enable [it] to review them in camera in order to assess if the Accused’s co-operation with the Prosecution could be regarded as being substantial”. The Trial Chamber then gave a substantive account of its analysis of the provided documents, before concluding that it could not itself assess them and therefore accepting the Prosecution’s assessment that the Accused’s co-operation was substantial.

62. The Appeals Chamber is convinced that, in order to provide a transparent assessment of the Appellant’s cooperation, a similar approach would have been appropriate in the present case, in particular in light of the reassurances given to the Appellant at the Sentencing Hearing.