(a) Any merchant may request a person on his premises to place or keep in full view any merchandise such person may have removed, or which the merchant has reason to believe he may have removed, from its place of display or elsewhere, whether for examination, purchase or for any other purpose. No merchant shall be criminally or civilly liable on account of having made such a request.
(b)  Any merchant who has reason to believe that merchandise has been taken by a person in violation of this act and that he can recover such merchandise by taking such a person into custody and detaining him may, for the purpose of attempting to effect such recovery or for the purpose of informing a peace officer of the circumstances of such detention, take the person into custody and detain him, in a reasonable manner and for a reasonable length of time.