Mo. Rev. Stat. § 540.320: Grand juror not to disclose evidence — penalty.

No grand juror shall disclose any evidence given before the grand jury, nor the name of any witness who appeared before them, except when lawfully required to testify as a witness in relation thereto; nor shall he disclose the fact of any indictment having been found against any person for a felony, not in actual confinement, until the defendant shall have been arrested thereon. Any juror violating the provisions of this section shall be deemed guilty of a class A misdemeanor.