Who knows what he does have in that hard drive. Maybe 4 months in prison is significantly better to what might happen if they do get to his data. Hell 4 months in jail because he refused to give a password sounds a lot better than a sexual offender conviction for 4 years.

In any case, if I was him I wouldn't worry about them decrypting the data in my lifetime. Do you know how many millions of years would it take to decrypt a 50 random char pass phrase decent encryption. Lots of those. So unless there is a breakthrough on computing power several magnitudes bigger than what we have experienced and the money to dedicate millions of computers to the cause, or someone finds a loophole in the encryption algorithm (highly unlikely if using any type of military grade encryption), his data won't be decrypted.