Mo. Rev. Stat. § 492.060: Persons deemed to have been lawfully sworn, when.

In all cases in which an oath or affirmation is required or authorized by law, every person swearing, affirming or declaring, in whatever form, shall be deemed to have been lawfully sworn, and to be guilty of perjury for corruptly and falsely swearing, affirming or declaring, in the same manner as if he had sworn by laying his hand on the gospels and kissing them.