The Jetson prototype can pick up on a unique cardiac signature from 200 meters away, even through clothes. Everyone's heart is different. Like the iris or fingerprint, our unique cardiac signature can be used as a way to tell us apart. Crucially, it can be done from a distance. It's that last point that has intrigued US Special Forces. Other long-range biometric techniques include gait analysis, which identifies someone by the way he or she walks. This method was supposedly used to identify an infamous ISIS terrorist before a drone strike. But gaits, like faces, are not necessarily distinctive. An individual's cardiac signature is unique, though, and unlike faces or gait, it remains constant and cannot be altered or disguised. Long-range detection A new device, developed for the Pentagon after US Special Forces requested it, can identify people without seeing their face: instead it detects their unique cardiac signature with an infrared laser. While it works at 200 meters (219 yards),