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Pointing Fingers

Polymer mixture that preserves both the pattern and the DNA from a bloody fingerprint

11 May 2021

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

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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