Does a police officer need to give a Miranda warning when the suspect is in custody?

judgment) ("An officer may not realize that a suspect is in custody and warnings are required. The officer may not plan to question the suspect or may be waiting for a more appropriate time."); see also Oregon v. Elstad, 470 U.S. 298, 308-09 ("It is an unwarranted extension of Miranda to hold that a simple failure to administer the warnings . . . so taints the investigatory process that a subsequent voluntary and informed waiver is ineffective for some indeterminate period.").