If you are being questioned regarding a crime which has been committed , ask them specifically if they have either "reasonable suspicion" , or "probable cause" to suspect you of committing said crime. If they say no, you do not have to give them your name, or answer any of their questions. If they say yes, say nothing except you want a lawyer, and NOTHING else. Car stops are different, if they stopped you in the first place, it's because you committed a traffic violation, and they already have probable cause. In that case, you are required to cooperate* i.e. give i.d., otherwise you could possibly face obstruction charges. But that does not mean you can't ask them why they stopped you, and you don't always have to submit to a search. It depends on the circumstances.