Missouri Revised Statutes Title XVII. Agriculture and Animals § 273.033. Killing or injuring a dog, reasonable apprehension of imminent harm is an absolute defense

1. In any action for damages or a criminal prosecution against any person for killing or injuring a dog, a showing by a preponderance of the evidence that such person was in reasonable apprehension of imminent harmful contact by the dog or was acting to prevent such imminent harmful contact against another person by the dog shall constitute an absolute defense to criminal prosecution or civil liability for the killing or injuring of such animal.

2. If a person has, on at least two occasions, complained to the county sheriff or to the appropriate animal control authority in his or her jurisdiction that a dog, not on a leash, has trespassed on property that such person owns, rents, or leases or on any property that constitutes such person's residence, and when at least one of the prior two complaints was motivated by reasonable apprehension for such person's safety or the safety of another person or apprehension of substantial damage to livestock or property, then any subsequent trespass by such dog shall constitute prima facie evidence that such person was in reasonable apprehension of imminent harmful contact. The county sheriff or animal control authority to which any complaint under this section is made shall notify the owner of the alleged trespassing dog of such complaint. Failure by a county sheriff or animal control authority to notify a dog owner under this subsection shall not invalidate or be construed in any way to limit any other provision of this subsection.

3. The court shall award attorney's fees, court costs, and all reasonable expenses incurred by the defendant in defense of any criminal prosecution or in 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.

4. This section shall not be construed to provide an absolute defense to a person who is engaged in or attempting to engage in a criminal activity at the time of the apprehension of imminent harmful contact, or to a person for any damage or injury to any person or property other than the dog itself that may result from actions taken in an attempt to injure or kill such dog.