His Miranda rights need to be read out loud to the suspect. Police officers always have to make sure the suspect knows his/her rights, and if the officer doesn't tell those rights, it would be considered unconstitutional like in the case Miranda vs. Arizona. Just in case you don't know the Miranda rights, here they are:
You have the right to remain silent. Anything you say will be used against you in a court of law. You have the right to have an attorney. If you cannot afford one, one will be appointed to you by the court. With these rights in mind, are you still willing to talk with me about the charges against you?
