Mo. Rev. Stat. § 473.063: Testimony to be recorded — record as evidence.

1. All the testimony adduced in support of any will shall be reduced to writing, signed by the witnesses and certified by the clerk.

2. The record of the testimony of any witness so certified is admissible in evidence in any action involving the validity of a will upon a showing that the subscribing witness is dead, mentally incapacitated or cannot be found.