I'm not as familiar as I used to be with Federal Law and the State I was an officer in, usually imposes stricter regulations upon law enforcement than the Federal Government does. Anyway, they are allowed to question him w/o advising him of his Miranda Right if the have cause to believe an imminent threat to the public still exists (
US v. Ferguson, 11-3806-cr 2nd Cir. 2012). This potential threat is self evident (e.g., potential for unexploded IEDs and/or their location, coconspirators who may be preparing to harm the public, etc.). The key word here is "imminent threat". Now, I believe it goes without saying that, all this information and "
just cause" will have to be shown in court during any trail.
Once (and if) the authorities are satisfied that no imminent threat exists, they will probably advise him of his Miranda rights before questioning him any further. They have more than enough physical evidence against him to charge him with several counts of murder, including his own brother's, not to mention the various terrorism related charges.
Still it will be interesting to see how it all unfolds in court once the attorneys get involved.