Mo. Rev. Stat. § 474.340: Nuncupative wills.

1. A nuncupative will may be made only by a person in imminent peril of death, whether from illness or otherwise, and shall be valid only if the testator died as a result of the impending peril, and must be:

(1) Declared to be his will by the testator before two disinterested witnesses;

(2) Reduced to writing by or under the direction of one of the witnesses within thirty days after such declaration; and

(3) Submitted for probate within six months after the death of the testator.

2. The nuncupative will may dispose of personal property only and to an aggregate value not exceeding five hundred dollars.

3. A nuncupative will neither revokes nor changes an existing written will.