Pointing Fingers

The traces we leave behind are fragile – DNA breaks up, blood dries, fingerprints fade. Without the luxury of a portable lab or huge quantities of fresh DNA, forensic scientists often face a compromise between science and sleuthing – preserve a perishing blood sample for hopeful DNA analysis or analyse the patterns that might be left in a fading smear or print. Yet here a cocktail of preserving chemicals react with the dried blood to fluorescently highlight the whorls and ridges of latent blood fingerprints left on aluminium foil (left) and painted wood (right). The polymer mixture, applied with a soaked cotton pad placed on top of a print, may work with prints that are over 600 days old, all the while preserving DNA in the blood, meaning genetic fingerprinting – comparing the sample’s DNA sequences to suspects or victims – may happen alongside more traditional forms of criminology.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Image adapted from work by Zhinan Fan and colleagues, in ACS Applied Materials & Interfaces 2021
• Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, P. R. China
• Image copyright held by the original authors
• Published in ACS Applied Materials & Interfaces, March 2021