Title : Alternate Light Sources
Content : Alternate Light Sources (ALS) can be used to reveal and photograph many forms of forensic evidence at the crime scene and in the lab. Physiological fluids (semen, urine, and saliva) can be found through their natural fluorescent properties utilizing UV light (365nm) or a blue light (455nm) viewed through an orange filter. Items such as bone fragments and teeth exposed with blue light (455nm) through the use of an orange barrier filter can be separated from the background for easy recovery. When using chemical development such as Ardrox, DFO, Cyanoacrylate with Basic Yellow, or dusting with fluorescent powders, blue (450nm-470nm) light with the appropriate barrier filter allows the investigator to capture the true evidence with little interference from lighting, background, or other masking factors. Even white light used at an oblique angle can help the investigator find and photograph hidden evidence such as dust prints on floors and indented writing on paper.
