Police unlock dead man's phone with his recreated fingertips

Last week, Rose Eveleth reported that police in Michigan asked a 3D printing lab to recreate a dead man’s fingers so they could unlock his phone and look for clues to who murdered him. Yes, we live in the future and it is weird.

This week, Michigan State University announced that its team of researchers led by Professor Anil Jain successfully unlocked the Samsung Galaxy S6. But they didn’t do it with the 3D printed fingers.

The police had copies of the man’s fingerprints from a previous arrest and the lab was able to scan them to make 2D and 3D replicas. Neither worked, so they decided to go back and improve the 2D version using a specially created computer program that was able to “fill in the broken ridges and valleys of the man’s prints.”

“We realized that the basic problem was the relatively poor quality of the fingerprints that were provided to us from the police files,” Jain said by email.

From MSU Today:

Once the fingerprints of the deceased were enhanced, Jain and his team printed new 2-D versions of the prints with conductive ink needed to create an electrical circuit just like live fingerprints do. According to Jain, smartphone fingerprint readers require an electrical circuit to unlock, which is why severed fingers won’t unlock a phone.

“Lucky for us, this phone did not require a passcode after a fixed number of failed attempts with fingerprints,” Jain said. “This allowed us to try different digitally enhanced fingerprints.”

Jain then asked Detective Rathbun to bring the phone back to his lab for another attempt to unlock it. This time, it worked.

“All of us just looked at each other,” Jain said. “And then we all shouted ‘it worked’ and started giving each other high fives.”

Jain told NPR that he “hopes this achievement will show the limits of fingerprint locks on mobile phones.”

This technique for breaking into phones, plus the fact that a “thought” like your passcode has more legal protections than a fingerprint, means that, when it comes to the authorities, a numerical passcode offers stronger protection of your phone’s contents than a fingerprint. Either way, though, police are supposed to get a warrant before snooping through your phone… unless you’re dead, in which case you no longer have a right to privacy.