I doubt this. Do you have a link to a paper covering this technique, or a conviction that used this technique?

Well you have information about the person including his name, perhaps hobbies, passwords from Google, Yahoo or other sites, which will provide them if they are fed some "terrorist threat, brown alert" mumbo-jumbo. In rest NSA and Choicepoint and help you on that front.

Then you just start building a customized keyspace from that information. Include some common substitutions: letters for numbers, numbers for letters. If you have other passwords, look for general patterns. Some people use long passphrases, but they have a pattern or algorithm on how they build all their passphrases! There you just might need a human expert to take a look.

In the end, yes, it is very difficult but it is still a lot better than plain brute-force.

But yeah, I doubt Customs have the equipment or knowledge to do this. That is something that NSA would do. They would have access to the best tools. I can imagine there might be some kind of very constrained cooperation between them. "You send us a disk clone + personal info of the owner, and we'll try to send you back the cracked passphrase. You don't ask as questions how we got it, and you don't even mention that we got involved at all."