(a) A private person who has been directed by a person he 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 paragraph (c) of this section, use physical force when and to the extent that he reasonably believes such to be necessary to carry out such officer's direction unless he knows or believes that the arrest or prospective arrest is not or was not authorized.

    (b) A private person acting on his own account may, subject to the limitations of paragraph (c) of this section, use physical force to effect arrest or prevent escape only when and to the extent such is immediately necessary to effect the arrest, or to prevent escape from custody, of a person whom he reasonably believes to have committed a crime and who in fact has committed such crime.

    (c) A private person in effecting an arrest or in preventing an escape from custody is not justified in using deadly force unless the use of deadly force is authorized under state or federal law.

    (d) The defendant shall have the burden of injecting the issue of justification under this section.

(Code 1964, § 7.670)

     State law reference(s)--Similar provisions, RSMo. § 563.051.