Cops Can Force You to Unlock Phone with Apple Touch ID, Judge Rules (huffingtonpost.com)

Makes sense. The fun will be when we have moderately accurate methods to extract information straight out of the brain (if your password is cAt and the prosecution shows you pictures of animals and see which parts of the brain lit when you see cow, dog and cat and guess that the password is feline in nature)

Then the fifth will have a hard time.