They can't use evidence gained directly from the hard drive during prosecution.
They can use evidence gained directly from the hard drive for the investigation.
It means they can't present stuff from the hard drive during the trial, but they can search the hard drive, find other people who communicated with her, and subpeona them for evidence, or get financial records and then subpeona banks for the evidence, etc.
It's an end-run around the 5th amendment. They are pretending that her participation in their prosecution won't be used against her directly, but it's OK if it will be used against her indirectly.
It's the same reason they don't always give you a
miranda reading prior to questioning:
Thus, if law enforcement officials decline to offer a Miranda warning to an individual in their custody, they may still interrogate that person and act upon the knowledge gained, but may not use that person's statements to incriminate him or her in a criminal trial.
So the judge believes that compelling her to provide evidence that might lead to additional evidence is ok, so long as the evidence she provides is not used in trial directly.
Unfortunately I don't know enough about this area of law to understand what else applies. If a criminal is caught in the act of destroying or hiding evidence, they can be charged with crimes related to that - but those crimes might be less punishing than the crimes they'd be convicted of if the evidence is found, so it might still be worth it.
If a building is locked, and is known to police to have relevant evidence, they can obtain a search warrant to open the building without the defendant providing the key - as long as they have the tools and techniques to do it.
The question is - can the defendant be forced to produce that key? The warrant gives them the right to the data contained in the hard drive, but without the key they don't have the proper tools and techniques to get into it.
If she doesn't provide it, can she be charged with something worse than obstruction of justice, or destruction of evidence? Are those charges worse than the charges she'd face if they had the data?
