In United States v. R. Enterprises, Inc. (1991) 498 U.S. 292, the Supreme Court rejected a lower court decision requiring the government to make an initial showing of relevancy, admissibility and specificity in order to enforce grand jury subpoenas for business records. "A grand jury subpoena is . . . much different from a subpoena issued in the context of a prospective criminal trial, where a specific offense has been identified and a particular defendant charged. . . . The Government cannot be required to justify the issuance of a grand jury subpoena by presenting evidence sufficient to establish probable cause because the very purpose of requesting the information is to ascertain whether probable cause exists. This Court has emphasized on numerous occasions that many of the rules and restrictions that apply at a trial do not apply in grand jury proceedings. This is especially true of evidentiary restrictions." (United States v. R. Enterprises, Inc., supra, 498 U.S. at p. 297-298.) "The teaching of the Court's decisions is clear: A grand jury 'may compel the production of evidence or the testimony of witnesses as it considers appropriate, and its operation generally is unrestrained by the technical procedural and evidentiary rules governing the conduct of criminal trials,' ." (Id. at p. 298.) "The law presumes, absent a strong showing to the contrary, that a grand jury acts within the legitimate scope of its authority. Consequently, a grand jury subpoena issued through normal channels is presumed to be reasonable, and the burden of showing unreasonableness must be on the recipient who seeks to avoid compliance. Indeed, this result is indicated by the language of Rule 17(c), which permits a subpoena to be quashed only 'on motion' and 'if compliance would be unreasonable' . To the extent that the Court of Appeals placed an initial burden on the Government, it committed error. . . ." (Id. at pp. 300-301.)