A police officer may stop and question a person at any time. They do not need to give a Miranda warning before informal questioning or before making an arrest. But any information gained this way is not admissible at a trial against the person. Miranda required advising a person of their rights before being question in police custody. If the person asks the officer if they are free to leave, they are not in custody. That is one of the few things a police officer may not lie about. During questioning police may use trickery, lying or other forms of deception in order to get a confession from a suspect. 