'Before' here means that the evidence will be formally considered or examined by the tribunal. See here:
https://dictionary.cambridge.o...onary/english/before
I agree with Ahmed's reply. The preposition "before" there has a meaning similar to "in front of one's eyes." For example, when I close my translations into English I write:
I DO HEREBY CERTIFY THE FOREGOING TO BE A TRUE, FULL, AND CORRECT TRANSLATION INTO ENGLISH OF THE COPY OF THE ORIGINAL DOCUMENT WRITTEN IN SPANISH WHICH I HAVE HAD BEFORE ME, TO WHICH I REFER, AND WHICH I ATTACH HERETO IN THE CITY OF ..., ON [DATE].