There’s a lot of talk around biometric authentication since Apple introduced its newest iPhone, which will let users unlock their device with a fingerprint. Given Apple’s industry-leading position, it’s probably not a far stretch to expect this kind of authentication to take off. Some even argue that Apple’s move is a death knell for authenticators based on what a user knows (like passwords and PIN numbers).
While there’s a great deal of discussion around the pros and cons of fingerprint authentication — from thehackability of the technique to the reliability of readers — no one’s focusing on the legal effects of moving from PINs to fingerprints.
Because the constitutional protection of the Fifth Amendment, which guarantees that “no person shall be compelled in any criminal case to be a witness against himself,” may not apply when it comes to biometric-based fingerprints (things that reflect who we are) as opposed to memory-based passwords and PINs (things we need to know and remember).
The privilege against self-incrimination is an important check on the government’s ability to collect evidence directly from a witness. The Supreme Court has made it clear that the Fifth Amendment broadly applies not only during a criminal prosecution, but also to any other proceeding “civil or criminal, formal or informal,” where answers might tend to incriminate us. It’s a constitutional guarantee deeply rooted in English law dating back to the 1600s, when it was used to protect people from being tortured by inquisitors to force them to divulge information that could be used against them.