"On Friday, Riana Pfefferkorn, cryptography fellow at the Stanford Center for Internet and Society, explored in an article for national security blog Just Security what this approach with exigent circumstances may look like. As well as noting it’s unclear whether judges would side with that law enforcement approach, Pfefferkorn highlighted that using exigent circumstances for iPhones in general, just in case they have USB Restricted Mode enabled (which should be, to note, on by default in the forthcoming iOS 12), is not really in the spirit of the legal mechanism.
“That is not how an exception to a rule works. 'Exigent circumstances' are supposed to be situational and case-specific. The DOJ’s own manual for electronic evidence search and seizure acknowledges as much,” she writes. DOJ’s manual says that “in electronic device cases, as in all others, the existence of exigent circumstances is tied to the facts of the individual case.”"