The Miranda warnings are designed to protect criminal suspects from the coercive nature of custodial interrogation. In a brief jointly filed with the National Association of Criminal Defense Lawyers, the ACLU argues that the police are not permitted to interrogate a suspect who has not expressly waived his Miranda rights and that there was no implied waiver in this case, assuming an implied waiver is ever permissible, because the defendant remained silent in response to the police interrogation for several hours before he ultimately confessed.