Most police investigators will try to get a suspect to waive their 5th Amendment right to remain silent. Most people believe that anything you say cannot be used against you if you have not been given your Miranda rights. This is false. Your words, statements, and confessions CAN be used against you.
The police follow a very simple process to get around giving citizens their Miranda rights. Miranda only applies if a suspect is in custody, and is not free to leave, or the suspect is under arrest. The police are very clever. If they suspect someone has committed a crime, they simply ask them or bring them down to the police station. The police will claim that the suspect was always free to leave. Sometimes the suspect is at the police station for 8 ,10 12 hours, and the police will later testify ,when in court, that the suspect was always free to leave, and as such, the police were not legally obligated to give the Miranda warnings.
Simply put, the police will first question you without arresting you. Once you give the confession you are released and then arrested. Miranda is a non-issue to police departments.