Quoted:
Why doesn't MO have civil immunity laws for people having to use self-defense?

Why doesn't MO place the burden on the prosecutor of disproving it was not self-defense?  Even California has this.

Sounds like this needs to change and to be contacting my Rep to see about this.

563.074.  Justification as an absolute defense, when. — 1.  Notwithstanding the provisions of section 563.016, a person who uses force as described in sections 563.031, 563.041, 563.046, 563.051, 563.056, and 563.061 is justified in using such force and such fact shall be an absolute defense to criminal prosecution or civil liability.
 2.  The court shall award attorney's fees, court costs, and all reasonable expenses incurred by the defendant in defense of any civil action brought by a plaintiff if the court finds that the defendant has an absolute defense as provided in subsection 1 of this section.

563.031

5.  The defendant shall have the burden of injecting the issue of justification under this section.  If a defendant asserts that his or her use of force is described under subdivision (2) of subsection 2 of this section, the burden shall then be on the state to prove beyond a reasonable doubt that the defendant did not reasonably believe that the use of such force was necessary to defend against what he or she reasonably believed was the use or imminent use of unlawful force.