What constitutes a Miranda warning for a defendant?

Miranda warnings are required only when a defendant is subject to custodial interrogation, meaning an interrogation that occurs when "'a person has been taken into custody or otherwise deprived of his freedom of action in any significant way.' [Citation.] Whether a person is in custody is an objective test; the pertinent inquiry is whether there was '"'a "formal arrest or restraint on freedom of movement" of the degree associated with a formal arrest.'"' [Citation.] [] . . . When reviewing a trial court's determination that a defendant did not undergo custodial interrogation, an appellate court must 'apply a deferential substantial evidence standard' [citation] to the trial court's factual findings regarding the circumstances surrounding the interrogation, and it must independently decide whether, given those circumstances, 'a reasonable person in [the] defendant's position would have felt free to end the questioning and leave' [citation]." (People v. Leonard (2007) 40 Cal.4th 1370, 1400.)