Here's a recording of the oral arguments for the US Court of Appeals, Third Circuit back in September:
http://www2.ca3.uscourts.gov/oralargument/audio/15-3537USAv....The gov's argument seems to be that because the defendant doesn't have to give the government the password but rather produce the decrypted hard drives, his actions aren't protected under the fifth. Analogy drawn with unlocking a safe.
EFF counter-argument to the safe analogy is that the encrypted documents do not simultaneously exist in a decrypted form protected by an obstacle, like a safe, but rather are produced as an act of translating the data from decrypted to unencrypted form; the government already has the data on the drives, they just can't understand it without the contents of the defendant's mind.
Justices then press the gov lawyer on whether there are fourth amendment issues in the case, as in whether the government can search all files on the hard drive, if decrypted, for evidence of criminality beyond the specific files they seek. Gov lawyer punts on the issue.
Basically it seems like a steep hill for proponents of encryption. The justices talk about how we're heading for a world where almost everything is encrypted, and encryption proponents are asking the government to give up an enormous amount of power.