From what I understand, under the Terrorism Act you're legally compelled to cooperate with the questioning and you're not allowed to remain silent so I have no doubt that those threats were real and that those questioning Mr. Miranda intended to act on said threats if they saw fit.
I'm no lawyer and I have no specific experience with the law in the UK, but I think the best path here is to shut the hell up and not answer anything until you get a lawyer. He was foolish to turn one down. You may be legally compelled to answer, but the consequences of your silence ultimately gets decided by a judge. I'd rather take my chances that the judge would rule it was a misuse of the Terrorism Act than trust some random cops with my passwords. And even if I were to fold under pressure, I'd do so with a lawyer's advice and not just because some goons threaten me.
At least, that's how I'd hope I'd behave, and that it wouldn't land me in Guantanamo without access to a lawyer or due process. I can certainly see how this kind of aggressive police tactic scares the shit out of people, and they may not know their options or be in a position to think about them clearly. And regardless of what the optimal approach was for Miranda, clearly this was a huge violation of his rights. "Know your rights" isn't a substitute for "they shouldn't abuse them".
But still: when you're detained and you're not sure what to do, default to silence.
According to the article he was offered a lawyer said no. You should basically never turn that down.
Also, if someone tells you that you don't have a right to silence, continue being silent. I know that's easy for me to say from where I'm sitting, but I'm pretty confident it's good advice, even in Heathrow Airport. At least give yourself a chance to beat the system.
If there was any encrypted material for which he didn't have the keys, as far as I understand legally they had enough to keep him. But then they probably worried how they would look like in public if it turns out to be only the preview of the film. He's still lucky he spent only 9 hours there.
Or maybe he was lucky if the material was prepared with:
The public-relations disaster that would come from arresting Greenwald's partner on the charge "he wouldn't answer our questions" would make the current flap look small, I think.
I read a source indicating that that's not quite true. Rather, if you don't answer questions at the time, the fact that you didn't can be introduced as evidence in trial later on. I.e., if the police pick you up and question you about a murder and you don't tell them your alibi, the government is free to mention that in court to imply that your alibi was created after the arrest.
This is explained in the standard British police caution:
> You do not have to say anything but it may harm your defence if you do not mention, when questioned, something which you later rely on in court. Anything you do say may be given in evidence.
There are, I believe (IANAL) quite specific rules around the use of 'adverse inference'[1], which is the way in which your lack of answers can be used.
On reading through the CPS guidance linked, the sheer complexity and number of potentially critical missteps someone unaware of the details could make is enlightening.
Say Nothing. Get a Lawyer. (Cue "Never talk to the police" youtube link... I wonder if there is a comprehensive UK equivalent?)
