A: You have the right to remain silent, so I would suggest that you always exercise that right; almost no one does themselves a service by speaking up and not exercising their right to remain silent. In most cases, everything you say works to your disadvantage and you regret what you say later on, especially if you’re the subject of the investigation.
The police must advise you whether you’re the subject of an investigation, so it pays to ask. If an officer is just looking for general information about whether a crime has been committed, it may be worth it to cooperate, but if the information they ask for is specific, especially if they’re narrowing things down to you, it always pays to speak to an attorney first, and to inform the officer of that desire.