It is the duty of all police officers to arrest any person detected in violation of any of the provisions of this chapter. It is further the duty of all such officers to make prompt investigation of any violation of the provisions of this chapter reported by any other person, and to cause a complaint to be filed before the proper court if there seems just ground for such complaint and evidence procurable to support the same.
(ILCS Ch. 625, Act 40 § 2-1)