Comment Like self-incriminating evidence in your safe (Score 2) 146
The only case where you are safe is when the information that you know the passcode is in itself incriminating.
An unknown person X hit Y over the head with their MacBook and killed them. The MacBook is locked with a password. The fact alone that you know the password means it's your MacBook and you are the murderer. Then they can't force you to unlock it, or can't use the fact that you know the password as evidence against you.
Or you bought a used hard drive on eBay. It's password locked. The police claims there is CP on it. You claim you don't know the password, you intended to reformat and use the drive. The fact that you know the password is evidence against you which cannot be used.