In March, two detectives went to a funeral home and asked to see a body. The reason? They wanted to unlock the man’s phone and needed his fingerprints, according to news reports. And though the detectives were granted access to the man’s body, they couldn’t unlock the phone.
The man, Linus Phillip, was shot and killed by a police officer outside a Wawa convenience store in Largo, Florida. Detectives were looking for information to help them investigate Phillip’s death as well as information about a separate investigation involving drugs, according to the Tampa Bay Times.
What the detectives did is legal, as Forbes reported, but it certainly raises ethical questions. And given that the detectives were unsuccessful, it resurfaces a science question as well: Do you need to be alive for your fingertips to unlock your phone?
In fact, it gets more difficult to unlock a phone using fingertips the longer a person has been dead, said Anil Jain, a professor of computer science and engineering who has spent years working on fingerprint recognition at Michigan State University and one of the authors of the “Handbook of Fingerprint Recognition” (Springer, 2009). [9 Odd Ways Your Tech Devices May Injure You].
This is because, on most smartphones, fingerprint identification works through electrical conductance, Jain told Live Science.
We all have a little bit of electricity running through our bodies. When we place our fingertips on a fingerprint scanner, the ridges of our fingerprint touch the surface whereas the valleys don’t. Tiny capacitors — devices that store electrical charge — will store more charge coming from the finger if they sit under ridges than they would under valleys. The sensors will use these patterns to form a detailed image. But when a person dies, that flow of electricity ceases, and with it, any chance of interacting with the scanner. Read more