Whether you are under investigation or have already been arrested, you have the Constitutional right to remain silent. You do not have to answer any questions from law enforcement. It is important to understand that anything you say to them can be used against you. The only question you may have to answer is to identify yourself. If you are pulled over by law enforcement in traffic, you will have to show your license, registration, and proof of insurance but you do not have to answer any questions in that situation either. You cannot be penalized for this.