In March of this year, two detectives in the United States arrived at a funeral home and asked to examine the body. Cause? They wanted to unlock the deceased man's phone, and they needed his fingerprints. Although they gained access to the body, the police were unable to succeed. This man, Linus Phillip, was shot and killed by a police officer outside the Wawa department store in Largo, Florida. The detectives were looking for information that could help them in the investigation of Phillip's death, as well as in a separate investigation on drugs.
Can a dead person unlock their phone?
What the detectives did is legal, but it certainly raises ethical questions. And given the fact that they have not been successful, there is also a scientific question: Do you have to be alive for your fingertips to unlock your phone? In fact, the longer a person has been dead, the more difficult it becomes to use their fingertips to unlock the phone. The reason is that, in the case of most smartphones, fingerprint identification works by electrical conduction.
How the fingerprint scanner works
There is some electricity inside every person's body. When you place the pad of your finger on the fingerprint scanner, the protrusions touch the surface of the scanner, while the “valleys” do not. Tiny capacitors (devices that store electrical charge) will get more charge where the protruding parts are than where the "valleys" are. The sensors use the received data to form a detailed image. However, when a person dies, electricity leaves his business, and with it, any possibility of interaction with the scanner. Scientists are not sure how long the body retains its electrical conductivity after death. It would take quite a few dead bodies to pinpoint this, and it would be necessary to use their fingers to try and unlock their phones every hour. It means,that someone will need to be in the morgue all the time. This is an extremely difficult experiment to carry out.
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Other versions of scanners
However, not all fingerprint scanners operate on the principle of electrical conduction. Older fingerprint scanners, for example, use optical sensors that measure changes in illumination between raised edges and "valleys" to form an image. However, this method is easier to cheat, since there is no electricity involved, so the system can be hacked without any problems. Moreover, technology is constantly changing. For example, consider the iPhone X, which doesn't have a dedicated fingerprint reader. It will unlock the phone by recognizing the user's face.
What will happen in the future?
The phones of the future will have optical sensors under their screens. It is not yet clear if it will be possible to access them with lifeless fingers, but conductivity in this case will not be an issue. Another new technology includes ultrasound scanners that send ultrasonic waves into the finger to measure stress patterns in protrusions and valleys. How such technology will interact with the fingers of dead people is also still unknown. One way or another, all of these sensors will be affected by the fact that the skin can change over time. If blood does not flow to the finger, microscopic wrinkles and cracks begin to appear on it. This will change the signals that the finger transmits to the sensor, and it will detect something that is completely different from what it was originally. Thus,scientists have yet to find a solution that would unlock the owner's phone after his death.
Marina Ilyushenko