I think Marcy Wheeler makes some important points about the possibility for abuse in the FBI's new Miranda guidelines, but I think she may be overly pessimistic.
The two claimed preconditions for torturing AZ–that he was a high ranking member of an international terrorist group and knowledgeable about operational details of pending terrorist operations–are exactly the same as two possible premises (of three) for delaying an American detainee's Miranda warning.
Only, with AZ, the CIA had to send John Yoo a bunch of information purportedly proving their claims before they got to torture AZ.
Look, I'd never take a bet against the authorities taking a mile when they've been given an inch. But I think it's inaccurate to compare this to the CIA and Abu Zubayda, because the CIA didn't have a functioning interrogation program before 9/11, and because the Miranda guidelines seem likely to apply here only in those cases where we're taking someone off of a plane with their underwear on fire. The FBI and CIA are very different agencies, and the FBI has given no indication that what it really needs in interrogations is more leeway to abuse suspects -- in fact, as I've said before, this memo seems, more than anything else, designed to solve a political problem: Republicans' meaningless obsession with Miranda.
Now, don't get me wrong. I'm not saying FBI Agents would use a Miranda delay to waterboard a detainee (waterboarding is CIA turf, after all). The CIA system clearly provided the opportunity for much more abuse.
But consider the one detainee known to be treated in such a fashion: Faisal Shahzad. The government claimed a central reason why they had to hold him without charge is that they needed unfettered access to him, 24/7, so they could immediately verify any new intelligence they picked up. Call me crazy, but interrupting a detainee repeatedly, 24/7, to ask a question sounds like a great way–even better than the Frequent Flier program used at Gitmo–to sleep deprive someone under the guise of doing something else. Since Shahzad eventually plead guilty (remember that Pakistan basically detained his family members, perhaps including his wife and kids, while he was being questioned), the judge never really challenged whether his confession was coerced.
I've seen no evidence that Shahzad was coerced or that he involuntarily waived presentment. But this seems to me to be incidental to Miranda. For someone in Shahzad's position, alerting their lawyer to the fact that they were threatened or coerced into giving a guilty plea would be the only way to reveal something like this, whether Miranda was given or not. And it's certainly possible for the feds to apply this kind of pressure even when a lawyer is present.
Like I said: I don't think Marcy is wrong to be worried, and I wouldn't bet against government abusing its power. But I don't see the new guidelines as being all that significant -- yet.