9. While it is true that, save for Rule 115(A) allowing parties to file supplemental briefs on the impact of the additional evidence admitted by the Appeals Chamber, no specific provision of the Rules explicitly regulates the possibility for the parties to supplement their briefs on appeal, it has been recognised in the jurisprudence that an appellant may supplement his or her brief, pursuant to Rule 127(A)(ii) and (B) of the Rules, by filing the said supplement with sufficient reasons constituting good cause for the Appeals Chamber to recognize it as validly filed.[1] In particular, the appellant must show that the proposed supplemental submissions are relevant to his grounds of appeal[2] and add substantial new information to the submissions which have already been made.[3]The new information at stake must be of sufficiently compelling importance to justify the admission of a supplemental brief at the stage where the briefing on appeal is completed.[4]

Footnote 42:

As concerns the Supplement [Supplement to Motion to Admit Additional Evidence, 2 December 2017] filed by Karadžić, the Appeals Chamber recalls that a party is to seek leave to file supplemental authorities. See Prosecutor v. Naser Orić, Case No. IT-03-68-A, Decision on Prosecution’s “Notice of Supplemental Authority”, 14 May 2007, p. 2. Furthermore, the Appeals Chamber finds that the Supplement, which concerns factual determinations based on a separate record reviewed by a separate trial chamber of the ICTY, does not present supplemental legal authority that would assist in the adjudication of the Motion.