The surface of polymer banknotes changes with use, and this affects fingerprint detection

What is it about?

The surface of polymer banknotes (currency bills) starts to crack and break up as the notes are handled. The different areas of the banknote, such as transparent regions and raised printing, behave differently. This also means that the effect is different depending on issuing bank. Familiar powder based fingerprint development techniques, and some chemical techniques, do not work well on the handled notes as the powder can be trapped on the surface. A metal evaporation process can be used to develop fingerprints from handled banknotes, and this is less affected by the surface cracking.

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Photo by Philip Veater on Unsplash

Photo by Philip Veater on Unsplash

Why is it important?

Choice of fingerprint development technique is affected by the material to be tested; fingerprints on paper and plastics, for example would have different optimum techniques. As more polymer banknotes are issued, forensic research has been conducted to find appropriate fingerprint development techniques. However, by necessity a lot of this has been done on mint notes as issued by banks. Our study shows that the handling of the banknotes has a significant effect, and this needs to be taken into account in choosing the appropriate technique, in order to reveal fingerprints.