Mo. Rev. Stat. § 58.420

When an inquest shall be continued by the coroner, it shall be his duty forthwith to call before him all witnesses summoned in the case, and verbally notify such as may attend to appear before him, to testify at the inquest on the day set for the continuance of the same, which verbal notice shall be in all respects as valid as a summons, and the coroner shall take note of the names of the witnesses so notified. No further summons shall thereafter issue to any witness so notified, and such notification shall have the same effect as an original summons, and may be the basis for an attachment of the witness.