The fact is that the police do not need a parent's permission or presence to question a minor child. In fact, they can take the child down to the police station and before a judge before notifying a parent that they have done this. That having been said, the police still have to give the Miranda warning (i.e. read them their rights) if they are in custody. In addition any statement that given must be voluntary and not the product of coercion and/or promises. Since this is a complex area of the law and you gave few details of the situation, you need to consult directly with a criminal law attorney in your are. they can best advise you further.