In both Miller and Selcraig, the Fifth Circuit held that, when the privilege applies, a party must provide substantial evidence that the sought-after information is relevant to overcome the privilege. Miller v. Transamerican Press, Inc., 628 F.2d 932, 932 (5th Cir. 1980); In re Selcraig, 705 F.2d 789, 792 (5th Cir. 1983). Regardless of whether the privilege exists in a particular case, however, the subpoenaing party always bears the burden of demonstrating that the material sought is relevant. United States v. Arditti, 955 F.2d 331, 345 (5th Cir. 1992).