> The judge in that case drew a bright line: Under the Fifth Amendment, police could not force the suspect to communicate his passcode, but they could force him to use his fingerprint to unlock the device. The reason?
> Providing a fingerprint was “non-testimonial,” because it did not require the suspect to produce anything from his own mind. On the other hand, to give up your personal passcode is classically testimonial, since it comes from your head.
https://www.aclu.org/blog/privacy-technology/surveillance-te...
Or, if they really wanted the phone unlocked, they could just follow the suspect and tackle him while he is using it.
https://arstechnica.com/tech-policy/2016/12/uk-police-unlock...