Do you agree or disagree with the Supreme Court’s majority ruling in Yarborough v. Alvarado?

Yarborough v. Alvarado (2004) was a civil liberties case decided by the US Supreme Court. The question before the court was whether a law enforcement officer needs to take into consideration certain subjective factors, such as the suspect's age and criminal history, in determining whether he or she is "in custody," for the purposes of reading them their Miranda rights.
In the landmark case of Miranda v. Arizona (1966), the Supreme Court ruled that law enforcement officers are required to inform an in-custody suspect of his or her constitutional rights, stated under the Fifth Amendment. If they fail to do this, then any subsequent statements made by a suspect will not be admissible in a court of law.
In Yarborough, the respondent, Michael Alvarado, was a young adult interviewed by police concerning his involvement in a crime. He wasn't formally arrested and he was not read his Miranda rights. Yet, during the interview, he confessed to his involvement in the crime. Subsequently convicted of second-degree murder and robbery, he appealed his conviction on the basis that, as he felt he was in custody, he was entitled to protection under the Fifth Amendment as established in Miranda. Initially, Alvarado was unsuccessful in his appeal but prevailed when his case came before the Ninth Circuit Court of Appeals. Yarborough then challenged the Court's verdict and the case was sent up to the US Supreme Court.
By a 5-4 majority, the Court ruled that the test of whether or not a suspect is in custody is an objective, not a subjective, one. In other words, even if the suspect genuinely believes that he or she is in custody, there still must be objective criteria in place to determine whether or not he or she actually is. It is only if these objective criteria are met that the police should read suspects their Miranda rights. Therefore, Alvarado's original criminal conviction was sound.
On the whole, I would argue that the Court's decision is correct. For one thing, it is an accurate interpretation of Miranda. The whole point of that ruling was to establish clear, objective standards that law enforcement officers could easily follow. Despite a good deal of criticism from the law enforcement community, there's evidence to suggest that Miranda has led to greater efficiency in the handling of cases and to a higher number of convictions as a consequence.
If subjective factors are taken into consideration, however, then the picture becomes somewhat blurred. Alvarado believed that he was in custody when in actual fact he wasn't. The Ninth Court of Appeals, in ruling in favor of Alvarado, held that young people of his age were more likely to feel that they were in custody and that subjective factors, such as his, were relevant in determining the necessary conditions for the reading of Miranda warnings.
The Supreme Court disagreed with this reasoning, and I would concur. Using subjective criteria such as a suspect's age simply adds confusion to an otherwise straightforward situation. If objective criteria can be established beforehand, then both law enforcement officers and suspects know exactly where they stand. Introducing subjective criteria into the mix makes it more difficult for everyone concerned to follow the correct procedure, potentially leading to both miscarriages of justice and criminals going free. The Supreme Court's ruling in Miranda related to the objective procedure of police interrogation, not the suspect's individual interpretation of what's going on. On that basis, I would argue that the majority of the Court made the correct decision.