The case centers around interpretation of the Fifth Ammendment. The Fifth Amendment says that nobody may be "compelled in any criminal case to be a witness against himself," which has become known as the right to avoid self-incrimination. But the Judge ruled that the Fifth Ammendment does not apply to a laptop saying "I find and conclude that the Fifth Amendment is not implicated by requiring production of the unencrypted contents of the Toshiba Satellite M305 laptop computer,"
What's the best analogy for the encryption password required to decrypt files? Is it the same as a key to a safe that itself holds incriminating documents? Defendants are already required to turn over such keys. On the other hand civil libertarians say that decrypting files you've encrypted is tantamount to giving self-incriminating testimony.
http://news.cnet.com/8301-31921_3-57364330-281/judge-americans-can-be-forced-to-decrypt-their-laptops/