Fingerprints and footwear forensics
Imaging
Imaging is a vital stage in the recovery of both fingerprint and footwear marks.
Imaging
There is no benefit in having a highly sensitive development technique if the marks cannot be imaged and supplied to an expert for analysis. HOSDB is investigating the potential of a range of imaging techniques that can be used for the capture of fingerprint and footwear marks- in laboratories and at crime scenes.
These techniques include infrared (IR) and ultraviolet (UV) imaging, where the mark is either imaged or illuminated outside the visible spectrum. Another technique being considered is multi-spectral imaging where lots of images are captured at differentwavelengths and combined into an 'image cube'. This technique can be used to separate fingerprints from multicoloured backgrounds, even where colour differences between the different regoins are minimal.
IR Imaging
Many inks used in printing are either reflective or transparent in the IR region of the spectrum. By using a filter that blocks visible but transmits IR radiation it is possible to use this effect to reveal fingerprints developed on some patterned backgrounds.
Multispectral Imaging
Multispectral imaging can also be used to reveal fingerprints against patterned backgrounds, but another potential application for multispectral imaging is in enhancing faint fingerprints. The colour spectrum for the developed fingerprint ridge can be identified and then all areas with this spectrum can be identifed, revealing portions of the mark not previously visible to the eye.
