If encryption is being used to hide "valuable criminal evidence", how is that different from someone hiding evidence by burying it somewhere or simply destroying it?
We don't detain random people and force them to give up locations of bodies they may or may not have buried, and we don't randomly search people's houses and posesssions -- and we shouldn't be doing the same for encrypted data (and this includes requiring backdoors). If there is other evidence to believe a particular person committed a crime, then get a warrant that compels them to give up the location of the body or the encryption key. If they refuse, then depending on the other evidence used for the warrant it might make sense to hold them in contempt.
In my mind, decrypting data to prove your innocence (in the face of other evidence) is vastly different than decrypting your data because law enforcement is on a fishing expedition (no other evidence).
[1] https://en.wikipedia.org/wiki/History_of_cryptography#Antiqu...
