While circumstantial evidence would suggest the cop who is being asked to decrypt his computer is in fact guilty of at the very least looking at child porn, we don't know concretely, yet he is being jailed until the judge decides that he really won't release the password. Imagine a less scrupulous judge and a more innocent man, maybe he's trying to protect the identity of source, suddenly it doesn't seem fair that the man should be jailed, yet in a world where we can compel you to release the password both cases are the same.
While circumstantial evidence would suggest the cop who is being asked to decrypt his computer is in fact guilty of at the very least looking at child porn, we don't know concretely, yet he is being jailed until the judge decides that he really won't release the password. Imagine a less scrupulous judge and a more innocent man, maybe he's trying to protect the identity of source, suddenly it doesn't seem fair that the man should be jailed, yet in a world where we can compel you to release the password both cases are the same.