Articles

A new application note examines the use of chemical treatments to enhance latent fingerprints on a dry porous surface such as a £20.

A widely used method of enhancement, DFO treated prints are located, viewed and then photographed under a high-intensity light source.

In the majority of cases a green (530nm) light sources can be used to excite the DFO treated print, however in the case of a £20 banknote this results in large amounts of background fluorescence from fibers within the banknote. This undesirable background fluorescence renders photography of prints impractical.

Now, due to the development of high intensity orange (590nm) light sources including the Crime-lite 82S and Crime-lite XL, it is possible to visualize DFO treated prints without inducing background fluorescence from the fibers within the note.

The images shown below are of a £20 banknote treated with DFO and illuminated with an orange Crime-lite 82S and have been captured using the DCS 4 fingerprint enhancement workstation.

 DFO is used to visualise fingerprints on a banknote Visible

A £20 banknote has been seeded with fingerprints and then treated with DFO. Circled in green, the two fingerprints can be seen as feint marks.

DFO is used to reveal latent fingermarks on a £20 note

Orange 590nm
Under the intense short-range illumination of the orange Crime-lite 82S the DFO treated fingerprints can be seen to fluoresce brightly with no background interference from the fibres in the banknote. Using the DCS 4 fingerprint enhancement workstation it has been possible to photograph the prints achieving clear ridge detail and high contrast.