Hmmmm... I was under the impression this was already the case. I remember reading about this a while ago when I was learning that they can force you to provide a fingerprint or face-scan.
Second, of course, don't keep evidence of crimes on your phone.
And final tip, on an iphone, hitting the lock button on the side five times rapidly will disable the biometric unlock until the passcode has been filled in. It also pops up with the option to call emergency services. Spamming the lock button is considered a panic button.