There's a vast difference between not cooperating and actively impeding. Destruction of inculpatory evidence, for example, is a crime, even if, by some definitions, destroying the evidence could be termed "not cooperating." That's why, IMO, the court makes a distinction between compulsory decryption of a drive which the prosecution already knows to contain incriminating data (which isn't testimonial, and hence not subject to 5th Amendment protection), versus being compelled to decrypt a drive because the government thinks it's likely to find incriminating evidence on it.
Actively impeding the prosecution, in the form of refusing to decrypt a drive known to contain inculpatory evidence, is in many ways tantamount to destroying that evidence. (Assuming, of course, reasonably secure encryption technology, &c.) You're not incriminating yourself by giving them the plaintext; they already know you have it, whether through confession, third party testimony, or some other means.
What the court is saying here, OTOH, is that it would be testimonial, and hence subject to 5th Amendment protection, for you to decrypt a drive the prosecution merely suspects to contain inculpatory evidence, however strong their argument for suspecting such evidence to exist (and they'll have much better arguments than, "Well, drive is big enough to hold millions of files..."). If they were to find any such evidence, they'd have found it through compelling you to provide it to them, and that's the thing they're saying is counter to the 5th Amendment — that, in providing them with evidence they didn't already specifically know to exist, you've incriminated yourself.
> is in many ways tantamount to destroying that evidence.
Nope. Doesn't fly. You imply that now that person can be jailed and held in contempt indefinitely until they comply.
Ok, so what if they forgot the password? What then? Forgetting the password is not the same as physically taking a hammer and destroying the hard drive. As far as the prosecution getting access to the documents, it has the same effect, but that is just that -- the same effect, it does not fall into the "knowingly destroying evidence" type action automatically.
So now you suggest that basically people can punished for forgetting. I see a big problem with that.
Moreover you give a (wrong) password and it doesn't work. You say "I am pretty sure that was right, to the best of my knowledge. I suppose I could have gotten it wrong, or maybe even the drive is damaged....." How do they know that this is a deliberate act? It seems here that lying to the police suddenly gives some degree of protection which strikes me as somewhat insane.
Indeed there have been cases in the UK where the defendant's apparent cooperation was enough to ensure there could be no RIPA prosecution even though the password to the encrypted hard drive did not seem to work. So this is not merely hypothetical.
I guess I disagree. Not generating evidence is different from destroying evidence; encrypting your laptop while you discuss drug deals is like wearing gloves while you steal the Hope Diamond.
Similarly, requiring you to actively aid in your own prosecution has no precedent. You can "lie by omission" while providing testimony, for example.
Not doing something to protect evidence is different from doing something to destroy evidence. If that's not the case, then every drug user has "destroyed evidence" of its possession by burning it and inhaling the fumes or by digesting it with their stomach acid.
encrypting your laptop while you discuss drug deals is like wearing gloves while you steal the Hope Diamond.
Disagree. The encrypted laptop contains evidence, in the form of emails, chat logs, or whatever, generated in the course of the discussion. Wearing gloves doesn't destroy evidence; it simply prevents its creation. Not logging your chats about drug deals would be the equivalent of wearing gloves while burgling; logging to an encrypted drive is something entirely different.
You can "lie by omission" while providing testimony
Not always. If you don't mention that you were watching your neighbor in the shower when you saw the defendant break into her apartment and kill her, no-one's going to bat an eye. If the omission is materially relevant to the matter at hand, and made with an intent to mislead, however, that's still perjury.
Imagine that we're talking about accounting fraud. The prosecution might be able to prove that the relevant accounting records exist, and have grounds to believe that these records would prove that fraud occurred, but not have the actual contents of the records themselves.
Child pornography is special, because merely having "possession" of certain information is a crime. The law itself is bizarre, so you get bizarre results like this.
> Honest question here: From a legal standpoint how can the" prosecution already knows [the harddisk] to contain incriminating data" if the drive is encrypted?
In many cases they can have intercepts, or bugs (cameras), but they are often not enough to form a water-tight case. They can therefore "know" you have incriminating data on your drive (or at least they will argue that point).