Mo. Rev. Stat. § 116.110: Signature may be withdrawn, when, how, effect, penalty.

Any voter who has signed an initiative or referendum petition may withdraw his or her signature from that petition by submitting to the secretary of state, before the petition is filed with the secretary of state, a sworn statement requesting that his or her signature be withdrawn and affirming the name of the petition signed, the name the voter used when signing the petition, the address of the voter and the county of residence. It is a class A misdemeanor punishable, notwithstanding the provisions of section 560.021 * to the contrary, for a term of imprisonment not to exceed one year in the county jail or a fine not to exceed ten thousand dollars or both, to knowingly file a false withdrawal statement with the secretary of state.