detail why he or she believes the subpoena is improper, unreasonable, or overly broad. Next, a judicial officer reviews those claims, determines whether the citizen’s constitutional rights are, in fact, implicated by the subpoena and, if so, balances those rights against the grand jury’s need for the requested information. As a starting point in its inquiry, however, the reviewing court must be mindful that a “presumption of regularity attaches to grand jury proceedings and hence to a grand jury subpoena.” In re Lopreato, 511 F.2d 1150, 1152 (1st Cir.1975). Accordingly, “[tjhose challenging such a subpoena have the burden of showing that irregularity exists.” Id. (citation omitted). See also United States v. R. Enterprises, Inc., 498 U.S. 292, 301, 111 S.Ct. 722, 112 L.Ed.2d 795 (1991) (<HOLDING>). With those principles in mind, then, this
holding that taxpayer who is the target but not the recipient of an administrative subpoena pursuant to 26 usc  7602 may challenge the subpoena holding that the burden of showing unreasonableness must be on the recipient who seeks to avoid compliance recognizing that the burden of persuasion for a showing of prejudice was on the defendant holding that a grand jury subpoena seeking a voice exemplar did not implicate fourth amendment rights but suggesting that even if it had at most the government would have been required to demonstrate that the grand jury subpoena was reasonable holding that because a grand jury subpoena issued through normal channels is presumed to be reasonable  the burden of showing unreasonableness must be on the subpoena recipient who seeks to avoid compliance but recognizing that a court may be justified under some circumstances in requiring the government to reveal the general subject of the grand jurys investigation before requiring the challenging party to carry its burden of persuasion