Police need reasonable suspicion to detain. Here, Officer Padilla was talking to a gang member when he saw Tirrez walking away, half-way down the block. Tirrez wore a San Francisco Giants jacket (which some gang members wear), talked on his cell phone, and had his other hand in his pocket. As Tirrez walked, he glanced back at the officer. Was there reasonable suspicion that Tirrez was involved in a crime?

A pat search is justified if an officer has the reasonable belief, based on articulable facts, that a person is armed and dangerous.  Here, Tirrez was in the Mission District, an area known for gang activity, with one hand in his jacket pocket.  The officer thought Tirrez’s hand was pushing the jacket pocket forward.  On these facts, could the officer reasonably believe that Tirrez was armed and dangerous?