A law enforcement agency has turned to a researcher at the University of Michigan for help in creating 3D replicas of a victim's fingerprints in order to gain access his phone. The technique, demonstrated earlier this year by Anil Jain, could help law enforcement unlock a device equipped with a fingerprint scanner.
While many modern fingerprint sensors require not only a fingerprint, but the electrical conductivity of a living finger, this technique is designed to get around that. From The Guardian:
First, the two-dimensional fingerprint scans are converted into three dimensional fingerprints and these are then sent to a high resolution 3D printer, to make a physical replica in a soft plastic that retains the subtle ridges of the fingerprint while also distorting under pressure like skin.
Once printed, a micron-thick coating of metal – gold, copper or silver – is applied to the surface. This recreates the electrical conductivity found in human skin that is required to make modern capacitive fingerprint readers work. Plastic fingers aren't conductive enough on their own.
The model of smartphone being targeted by law enforcement wasn't disclosed, nor what exactly police are hoping to find on the device. You can see the technique in action in the video below.