In order for police to do a search what must they have?

Police officers are specially trained to read body language. If they think someone is acting strangely around their presence, for example avoiding eye contact or walking quickly, then officers have the power to stop and search that person on suspicion on criminal activity. They will ask that person for their details and to identify themselves too, in case there is an outstanding warrant on them.

They do it to protect you, the member of public, from harm.