A Virginia judge ruled that police can force a criminal defendant to unlock their phone using a fingerprint, but a defendant can't be forced to give up a passcode when Touch ID or similar technology isn't set up to open the device.

The case that Virginia Beach Circuit Court Judge Steven Frucci ruled over involves Emergency Medical Services captain David Baust, who was charged with trying to strangle his girlfriend earlier this year. Prosecutors in the case said that Baust's smartphone may contain video of the incident, and sought to get Frucci to force Baust to unlock his phone, which may or not be protected by either a fingerprint or passcode. Baust's attorney argued that the information used to open a device is protected by the Fifth Amendment. (The Fifth Amendment protects people from giving up knowledge that could lead to self-incrimination). 

Frucci, however, pointed out that the Amendment protects knowledge, and not something like a physical fingerprint—which law enforcement can compel Baust and other criminal defendants to give up, just as they would a DNA sample for evidence. Yet, if Baust's phone requires two-steps to unlock it, such as requiring a fingerprint and a passcode, then his phone would remained unlocked and police won't be able to access it using those means. 

The Baust trial can give judges involved with locked electronics a model to use in future cases. So far, having a passcode for your phone or the encrypted files on your computer won't always protect you, as cases in Florida and Vermont show. In the 2011 Florida case, an unidentified man had two computers and five external hard drives seized during a child pornography investigation. Because his files were encrypted, the judge said forcing him to give up the passcodes will violate the Fifth Amendment. Yet, in a 2009 Vermont case, police found child pornography on a man's computer, but later realized after seizing the device that portions of it was encrypted. The man tried using the Fifth to escape giving up his passcodes, but the judge declined, saying that officers already knew what the information was on the computers, and that his not giving up the passcodes was merely obstructing access to evidence.