The Supreme Court ruled in Miranda v. Arizona that the police must advise individuals of their rights at that time they are taken into custodial arrest. In effect, at the time they are detained and when police questioning turns from general information gathering of an individual to accusatorial interrogation, that is when the Miranda warnings must be given. The warnings are a product of the Fifth Amendment right against self-incrimination.
With Dzhokhar A. Tsarnaev, the police were within the Constitution not to read him his rights when they first apprehended him. They needed to determine if he had bomb or other weapons that could threaten police or public safety. Once that threat was addressed t hey should have Mirandized him. It would have taken a few seconds and no harm would have followed form doing that.
There is little evidence that Mirandizing someone really hurts a police case, but not doing so can be significant. In general information gathered in violation of the Miranda requirement cannot be used in Court to convict a person. Thus, potentially information that the police gather on Dzhokhar A. Tsarnaev might not be allowed in court to prosecute him. A review of post-Quarles cases does not make it clear what the public safety exception will allow in.
But would it not be better not to take a chance. Why risk prosecution by not giving him his rights? Depending on what he is charged with and what evidence there is, this decision could be legally damaging to the government's case.
For the most part, the Supreme Court rejected the Bush Administration's questionable legal theories. In a series of cases most notably including Hamdi v. Rumsfeld, 542 U.S. 507 (2004), the Court ruled that all individuals--not just American citizens--held within US territories, must receive the protection for their rights that the Constitution demands. Yet despite these rulings, both Bush and now Obama have continued to press these flawed legal theories. Most recently, the Obama Administration pressed the case to support Drone warfare, and now this use of the public safety exception with Tsarnaev.
Presidents do not have extra-constitutional power. Respect for our constitutional rights is not something we do when it is just convenient. It is something that is required of a democratic free society. It is what separates the US from non-democratic countries. Tsarnaev is a US citizen arrested and accused of crimes in this country. There is no reason to exempt him from the Constitution. In a free society the government carries the burden to prove guilt and it is required to play by the rules. The rule should apply here to.