What authority does a police officer have to search and seize a gravity knife?

authority that relates to when, exactly, a police officer has reasonable cause to search and seize a gravity knife. In People v. Brannon, 16 N.Y.3d 596, 925 N.Y.S.2d 393, 949 N.E.2d 484 (2011), the defendant was walking along a street in Manhattan. A police officer stopped defendant and seized what turned out to be a gravity knife. The officer described that he could see the hinged part of a knife in defendant's back pocket. Upon approaching closer to defendant, the officer saw the outline of a knife through the material of defendant's back pocket. The officer testified that the knife looked like a typical pocket knife. Upon questioning, defendant admitted he had a knife. The officer then frisked defendant and recovered what turned out to be a gravity knife.