What is the test for whether a person in custody is entitled to leave the police car?

Appellant further asserts that she did not believe she could leave the patrol car. And because she had confirmed the dead body discovered in her backyard was her missing father, she argues that no reasonable person in her position would have felt free to leave. But appellant's subjective belief (like the sergeant's) is irrelevant to the determination of whether a person is "in custody," which "depends on the objective circumstances of the interrogation, not on the subjective views harbored by either the interrogating officers or the person being questioned." (Stansbury v. California (1994) 511 U.S. 318, 323.)