He took the store employee at his/her word. Why not the accused? The cop just showed up after the fact and tased the woman. Truth of the matter is you should never talk to a cop without an attorney present for except to give basic information like your name and address.
Yes, because showing him her ID and the receipt showing that she did shop at that store and purchased things, that would necessitate a lawyer. If she co-operated in the slightest, she would have been on her way.