Missouri Revised Statutes Title XXXVIII. Crimes and Punishment; Peace Officers and Public Defenders § 563.051. Private person’s use of force in making an arrest

1. A private person who has been directed by a person he or she reasonably believes to be a law enforcement officer to assist such officer to effect an arrest or to prevent escape from custody may, subject to the limitations of subsection 3 of this section, use physical force when and to the extent that he or she reasonably believes such to be necessary to carry out such officer's direction unless he or she knows or believes that the arrest or prospective arrest is not or was not authorized.

2. A private person acting on his or her own account may, subject to the limitations of subsection 3 of this section, use physical force to arrest or prevent the escape of a person whom such private person reasonably believes has committed an offense, and who in fact has committed such offense, when the private person's actions are immediately necessary to arrest the offender or prevent his or her escape from custody.

3. A private person in effecting an arrest or in preventing escape from custody is justified in using deadly force only:

4. The defendant shall have the burden of injecting the issue of justification under this section.