Big question is whether turning over the passphrase would be "testimonial". I could see it being argued that it's a forgone conclusion he owns these bitcoins -

Big question is whether turning over the passphrase would be "testimonial". I could see it being argued that it's a forgone conclusion he owns these bitcoins -- enough evidence to tie him to silk road, and evidence in the block chain showing those coins came from silk road. (This is relevant due to the fifth amendment to the constitution. In many cases, turning over a password or combination is considered self incrimination and thus cannot be compelled by the state.)