11.7: Infra-Red

Infra-Red

The infra-red (IR) spectrum is very useful to the forensic technician when examining dark colored clothing and fabrics. Infra-red imaging occurs between 700nm and above. You will, however, need a DSLR camera that has been altered to photograph only in the infra-red spectrum (this is done by removing the IR blocker from the camera’s sensor). Outdoor imaging and image captures are not a problem as the sun provides plenty of IR light for the camera’s sensors. Indoors, however, the technician will need to bring an IR light source as LED, fluorescent, and tungsten lighting do not emit IR.

A uniform shirt as visualized by the naked eye and by IR imaging. Author's collectionging. Author's collection

In the above photographs, not only are you better able to visualize the stab defects on the shirt, but your author was also able visualize the saliva of the suspect on the shoulder patch. It should also be noted that by preserving the shirt in waxed butcher paper, your author was also able to recover several hairs that provided a DNA match to the suspect. It is essential to take a context photograph in visible light of the item you are photographing before taking the IR photograph as you will need to explain to the jury the difference between the two images.