The Times obtained the text of an F.B.I. memorandum I discussed yesterday that effectively expands the public safety exception to Miranda in cases of terrorists. The memorandum provides three steps to follow. The first two hew closely to Supreme Court precedents:
1. If applicable, agents should ask any and all questions that are reasonably prompted by an immediate concern for the safety of the public or the arresting agents without advising the arrestee of his Miranda rights. 
2. After all applicable public safety questions have been exhausted, agents should advise the arrestee of his Miranda rights and seek a waiver of those rights before any further interrogation occurs, absent exceptional circumstances described below.
Generally speaking, the public safety exception only permits the abrogation of Miranda for imminent threats. But the third step the memo provides expands this exception.
3. There may be exceptional cases in which, although all relevant public safety questions have been asked, agents nonetheless conclude that continued unwarned interrogation is necessary to collect valuable and timely intelligence not related to any immediate threat, and that the government’s interest in obtaining this intelligence outweighs the disadvantages of proceeding with unwarned interrogation. 
The memo includes Footnote Four which lists a number of opinions showing that 5th Amendment violations only occur if evidence is admitted at trial. I don’t think any of these cases permit interrogations without Miranda in circumstances without an imminent threat:
The Supreme Court has strongly suggested that an arrestee’s Fifth Amendment right against self-incrimination is not violated at the time a statement is taken without Miranda warnings, but instead may be violated only if and when the government introduces an unwarned statement in a criminal proceeding against the defendant. See Chavez v. Martinez, 538 U.S. 760, 769 (2003) (plurality op.); id. at 789 (Kennedy, J., concurring in part and dissenting in part); cf. also id. at 778-79 (Souter, J., concurring in the judgment); see also United States v. Patane, 542 U.S. 630, 641 (2004) (plurality opinion) (“[V]iolations [of the Fifth Amendment right against self-incrimination] occur, if at all, only upon the admission of unwarned statements into evidence at trial.”); United States v. Verdugo-Urquidez, 494 U.S. 259, 264 (1990) (“[A] violation [of the Fifth Amendment right against self-incrimination] occurs only at trial.”)
That footnote is somewhat misleading, as it does not support the proposition. It just explains that even if Miranda is violated, if the US doesn’t introduce it at trial, it’s cool.
Step three concludes by suggesting “whenever feasible” that the agent obtain permission from the FBI or DOJ.
Whenever feasible, the SAC will consult with FBI-HQ (including OGC) and Department of Justice attorneys before granting approval. Presentment of an arrestee may not be delayed simply to continue the interrogation, unless the defendant has timely waived prompt presentment.
As I commented previously, this memorandum seems to expand the Supreme Court’s interpretation of the public safety exception beyond the imminent threats in Quarles to cases where the agent determines that it is important to “collect valuable and timely intelligence not related to any immediate threat.” No Supreme Court precedents to support that. I’ll repost my earlier comment:
Is it that simple? If the government does not seek to use the evidence in Court, they can ignore the Constitutional right? Isn’t the point of Miranda to deter police misconduct–not just to prevent its admission in Court. I don’t think the US would need whatever statements the Christmas Day bomber made in order to convict him. Thus, with impunity, they could ask any sorts of questions notwithstanding Miranda, and convict him just the same. It seems they can have their cake, and eat it too.
This position really seems to defeat the purpose of Miranda. I suppose one day the Court will have a chance to opine on this issue. But how? There won’t be a motion to suppress because these statements will never be introduced. Perhaps under a 1983 action for violation of civil rights? That won’t get very far. Perhaps a due process challenge? It seems any proceeding would be collateral to the conviction. In essence, this action is shielded from any meaningful judicial review (I think).