42. The Appeals Chamber finds that it is in the interests of justice to examine proprio motu whether the material tendered by the Prosecution in its Motion of 7 September 2006 can be admitted as rebuttal evidence on appeal. It has been well established by the jurisprudence that rebuttal material is admissible if it directly affects the substance of the additional evidence admitted by the Appeals Chamber[1] and, as such, has a different test of admissibility from additional evidence under Rule 115 of the Rules.[2] In light of its findings above with respect to the admissibility of the Additional Statement, the Appeals Chamber finds that copies of envelopes in which the copies of the Additional Statement were purportedly sent to various addressees within the Office of the Prosecutor are directly relevant to the issue of the authenticity of the Additional Statement and a fortiori that of the Recantation Statement. Therefore, the Appeals Chamber is satisfied that the proffered material affects the substance of the admitted additional evidence and is thus admissible as rebuttal evidence on appeal.