Each person’s fingerprint is unique, so it is used a lot for important documents such as work contracts, citizen identification, …. And because of that uniqueness, each person’s fingerprint is also used as a phone password.
But in some cases, why is it not possible to use the fingerprint of the deceased to open their personal electronic devices?
This is because most smartphones recognize fingerprints through the conductivity of the finger. We all have a small electrical current running through our bodies. When touching the fingerprint scanner part of the phone with our finger, only our fingerprint touches it, and the finger grooves do not.
Currents from the ridges will hit and tiny capacitors (charge storage devices) will capture these charges and reconstruct them into a detailed image. But when people die, the cells will stop working and this current will gradually disappear, making it impossible for us to unlock the phone with fingerprints anymore. However, how long after death this current completely disappears remains a mystery.
Electronic device that recognizes fingerprints through the electrical conductivity of the finger.
Besides, when dead, the fingers will appear wrinkles or shriveled because there are no more blood vessels running through, making the fingerprints different from the old one and also unable to unlock.
If the fingerprints are changed after death, how can the coroner determine the identity of the deceased? That’s thanks to a technique called Thanatopractical Handling – the study was published November 5, 2013 in the journal GMS Interdisciplinary Reconstructive and Reconstructive Surgery. This technique uses a liquid extracted from other parts of the body to restore tension and volume in the fingers. Of 400 bodies decomposing at different stages, the method was able to get fingerprints in three-quarters of the cases and was able to eliminate matches in at least 11% of the remaining cases.