Sequential processing strategies for fingermark visualisation on uncirculated £10 (Bank of England) polymer banknotes

Area of Science:

• Forensic Science
• Trace Evidence Analysis
• Biometrics

Background:

• Polymer banknotes present unique challenges for fingermark visualization due to their non-porous surface.
• Established fingermark development techniques require evaluation on novel substrates like the Bank of England's £10 polymer notes.
• Aging of fingermarks can significantly impact their detectability.

Purpose of the Study:

• To compare the effectiveness of five distinct fingermark visualization process sequences.
• To assess fingermark quality on new, uncirculated £10 polymer banknotes from the Bank of England (BoE).
• To determine optimal sequences and individual processes for enhancing fingermarks on polymer substrates.

Main Methods:

• Eight new £10 polymer banknotes were used, each with 64 natural fingermarks.
• Half the marks were aged 2-3 days, the other half 12-13 days.
• Fingermarks were visualized using five different process sequences and assessed under primary (visible light, fluorescence) and secondary (infrared, UV reflection, gelatin lifting) viewing conditions.

Main Results:

• Sequence 4 (92.2%) and Sequence 3 (89.1%) yielded the most identifiable fingermarks across all assessment conditions.
• Black magnetic powder, when imaged with reflected infrared, was the most effective single process (82.8%).
• Sequence 1 excelled for fresh marks under visible light conditions.

Conclusions:

• Specific fingermark visualization sequences demonstrate high effectiveness on new £10 polymer banknotes.
• The use of secondary viewing conditions, particularly infrared reflection, significantly enhances fingermark contrast and identification.
• Further research is needed on the sensitivity of these processes and their performance on circulated, worn polymer banknotes.