(2) Directed by a Public Servant. A person who has been directed by a public servant to assist that public servant is justified in 'using force to carry out the public servant's direction, unless the action being taken by the public servant is plainly unlawful.
(3) Citizen's Arrest. A person is justified in using force upon another in order to effect his arrest or prevent his escape when a public servant authorized to make the arrest or prevent the escape is not available, if the other person has committed, in the presence of the actor, any crime which the actor is justified in using force to prevent or if the other person has committed a felony involving force or violence.