1) A lot of people assume that the police are required to read a suspect his Miranda rights upon arrest. That is, they assume that one of a person’s rights is the right to be read their rights. It often happens that way on Law & Order, but that’s not what the law actually requires. The police aren’t required to follow Miranda. Miranda is a set of rules the government can chose to follow if they want to admit a person’s statements in a criminal case in court, not a set of rules they have to follow in every case. Under Chavez v. Martinez, 538 U.S. 760 (2003), it is lawful for the police to not read a suspect his Miranda rights, interrogate him, and then obtain a statement. Chavez holds that a person’s Miranda rights are violated only if the statement is admitted in court, even if the statement is obtained in violation of Miranda. See id. at 772-73. Further, the prosecution is even allowed to admit any physical evidence discovered as a fruit of the statement obtained in violation of Miranda — only the actual statement can be excluded. See United States v. Patane, 542 U.S. 630 (2004). So, contrary to what a lot of people think, it is legal for the government to even intentionally violate Miranda so long as they don’t try to seek admission of the suspect’s statements in court.

2) Even if we assume that the police later seek to admit a statement from Tsarnaev from post-arrest custodial interrogation outside Miranda, a court would allow an initial pre-Miranda interrogation to be admissible under the public safety exception of New York v. Quarles, 467 U.S. 649 (1984). It’s not clear how long the public safety exception will continue to apply: At some point in time, it becomes harder to say that the agents needed to dispense with Miranda in light of the threat to public safety. We don’t have good cases on when that line might be crossed, in part because (fortunately) there aren’t many similar cases. So the longer investigators interrogate Tsarnaev outside Miranda, the more they run the risk that some statements they obtain from him may be inadmissible. But recall that under (1), the government is still free to question Tsarnaev outside Miranda as long as the government accepts the uncertainty of whether those statements would be admissible in a criminal case against him. Assuming that the evidence against Tsarnaev’s many different crimes over the last week is likely to be overwhelming, agents may not need any statements from him for a criminal case. They may simply want whatever intelligence he can provide for use in broader antiterrorism efforts, and Miranda is no impediment in that case. The agents are free to question Tsarnaev outside Miranda to gather intellligence as long as they don’t cross the line into coercing statements from him. See, e.g., Townsend v. Sain, 372 U.S. 293 (1963).