Mo. Rev. Stat. § 115.539
If the court finds there is a prima facie showing of irregularities which place the result of the primary election in doubt, the court shall order a recount of all votes brought in question by the petition or its answer. Where the issue is drawn over the validity of certain votes cast, a prima facie case is made if the validity of a number of votes equal to or greater than the margin of defeat is placed in doubt. The court may order a recount of all votes brought in question by the petition or its answer at any time if it finds that the primary election result is placed in doubt. All materials and records relating to the contested election may be subpoenaed and all information contained therein shall be subject to the rules of discovery in civil cases. During a recount, the court may hear additional evidence offered by any party bearing on any issue relating to the contested election.
§ 115.539, RSMo
Effective 1/1/1978