The difference is described here in Orin Kerrs reversal of his opinion earlier today: https://www.washingtonpost.com/news/volokh-conspiracy/wp/2015/09/25/a-rev

The difference is described here in Orin Kerrs reversal of his opinion earlier today: https://www.washingtonpost.com/news/volokh-conspiracy/wp/2015/09/25/a-revised-approach-to-the-fifth-amendment-and-obtaining-passcodes/ https://www.washingtonpost.com/news/volokh-conspiracy/wp/201... Basically, having to provide something in your mind, the passcode, is testimony, a finger print, much like a key, is not testimony.