Trial subpoenas commanding a witness to appear at trial and produce documents are governed by different rules than discovery subpoenas.
Specifically, Sections 491.090-491.100, RSMo “confer upon [a] litigant the right to require the production of any document a litigant believes necessary to meet the issues raised in the action.” State ex rel. Rowland Group v. Koehr, 831 S.W.2d 930, 933 (Mo. 1992). The only limitation with respect to the document requests are that they must not be “unreasonable and oppressive.” State ex rel. Filkey, Inc. v. Scott, 407 S.W.2d 79, 84 (Mo. Ct. App. 1966).
Whether something is unreasonable and oppressive for purposes of Section 491.100, RSmo is within the discretion of the trial court. Koehr, 831 S.W.2d at 933.