23. Furthermore, the Appeals Chamber does not agree with the United States that the necessity requirement under Rule 54bis stipulates that an applicant must make an additional showing that the requested materials in fact exist.[1] The necessity requirement obliges the applicant to show that the requested materials, if they are produced, are necessary for a fair determination of a matter at trial. Requiring an additional showing of actual existence would be unreasonable and could impinge upon the right to a fair trial given that these materials are State materials, often of a confidential nature. In many cases, it would be impossible for an applicant to prove the existence of these materials. All that is required is that an applicant make a reasonable effort before the Trial Chamber to demonstrate their existence. […]