mere presence at a police station may not be sufficient, but neither is such a presence required. Traffic stops are not deemed custodial. The Court has ruled that age can be an objective factor. In Yarborough v. Alvarado (2004), the Court held that "a state-court decision that failed to mention a 17-year-old's age as part of the Miranda custody analysis was not objectively unreasonable". In her concurring opinion Justice O'Connor wrote that a suspect's age may indeed "be relevant to the 'custody' inquiry"; the Court did not find it relevant in the specific case of Alvarado. The Court affirmed that age could be a relevant and objective factor in J.D.B. v. North Carolina where they ruled that "so long as the child's age was known to the officer at the time of police questioning, or would have been objectively apparent to a reasonable officer, its inclusion in the custody analysis is consistent with the objective nature of that test". The questioning does not have to be explicit to trigger Miranda rights. For example, two police officers engaging in a conversation designed to elicit an incriminating statement from a suspect would constitute questioning. A person may choose to waive his Miranda rights, but the prosecution has the burden of showing that such a waiver was actually made. A confession not preceded by a Miranda warning where one was necessary cannot be admitted as evidence against the confessing party in a judicial proceeding. The Supreme Court, however, has held that if a defendant voluntarily testifies at the trial that he did not commit the crime, his confession may be introduced to challenge his credibility, to "impeach" the witness, even if it had been obtained without the warning. In Hiibel v. Sixth Judicial District Court of Nevada (2004), the Supreme Court ruled 5–4 that being required to identify oneself to police under states' stop and identify statutes is not an unreasonable search or seizure, and is not necessarily self-incrimination. Explicit invocation In June 2010, the Supreme Court ruled in Berghuis v. Thompkins that a criminal suspect must now invoke the right to remain silent unambiguously. Unless and until the suspect actually states that he is relying on that right, police may continue to interact with (or question) him, and any voluntary statement he makes can be used in court. The mere act of remaining silent is, on its own, insufficient to imply the