Biomedical Engineers Discover Pruny Fingers Yield the Same Fingerprint Patterns as Dry Ones
A question posed by a child in a Curious Kids column in The Conversation, a nonprofit news website written by academics, led a biomedical engineer to a discovery that could aid forensic analysis at crime scenes involving water exposure.
Guy German, a biomedical engineer at Binghamton University in New York, writes for Curious Kids and conducts research funded by the National Science Foundation. When a 12-year-old boy from Washington state asked why fingers and toes get wrinkly and change color after a dip in a pool or bath, German and his team, who study the mechanics and function of soft biological tissues, set out to investigate.
In a paper published in the May issue of the Journal of the Mechanical Behavior of Biomedical Materials, German and Rachel Laytin demonstrate that the topography patterns of fingerprints remain consistent after multiple immersions in water. When fingers wrinkle in water, it is because the autonomic nervous system triggers blood vessel constriction, causing the skin’s outer layer, the stratum corneum, to buckle while underlying structures remain stable. This results in consistent wrinkle patterns each time, potentially an evolutionary adaptation to improve grip in wet conditions, similar to tire treads.
German and Laytin tested this by having participants immerse their fingers in water for 30 minutes, photographing the wrinkles, and repeating the process a day later. They found the same loops and ridges of wrinkles in each trial, despite variations in skin thickness influencing wrinkle depth across individuals.
They also discovered that individuals with nerve damage in their fingers do not develop wrinkly skin after water exposure, confirming the autonomic nervous system’s critical role in this process. This finding could assist forensic labs in identifying individuals using fingerprints at crime scenes where victims have been exposed to water, as consistent patterns enable reliable matching of wet and dry prints. Additionally, the absence of wrinkling may aid medical diagnostics by indicating autonomic nervous system disorders, such as those seen in diabetes or Parkinson’s disease.
What began as a simple childhood question about pruny fingers has led to surprising truths with far-reaching implications. German and Laytin’s research not only confirms the remarkable consistency of fingerprint patterns through water exposure but also uncovers a potentially revolutionary forensic tool. Their findings suggest that even waterlogged crime scenes—long considered challenging for fingerprint analysis—may now yield identifiable evidence, closing cases that once seemed unsolvable.
Source: Forensic Magazine
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