This article reports on the National Institute of Justice's (NIJ's) Forensic Technology Center of Excellence's (FTCoE's) "Landscape Study of Alternate Light Sources," which provides a basic understanding of the technology's uses, benefits, and limitations.
Although ALS technology has been used for a number of years, recent innovations have contributed to a crowded and sometimes confusing market, which offers just over 50 devices. Recent developments in ALS technology have produced portable, hand-held devices that can be used by one person. Photography at a crime scene can be greatly improved by using its capabilities. The ALS causes certain materials to fluoresce, which improves the visualization of certain evidence. Evidence illuminated by these light sources can be viewed by using a barrier filter, such as goggles, and can be documented for court purposes with a standard digital camera equipped with an appropriate filter. Consistent improvement in ALS has occurred with the use of LEDs, better filters, and reduced battery size. Products range from small hand-held flashlights that use only one wavelength to a shoebox-sized ALS that uses 16 or more wavelengths. Cost can range from $20 to over $10,000. ALS devices are most commonly used in crime-scene investigations, forensic biology, latent prints, trace evidence, medico-legal death investigation, and forensic nursing. The study report provides illustrative scenarios for each type of ALS use. ALS devices included in the scenarios emit light in the visible and ultraviolet regions of the electromagnetic spectrum. The report notes that ALS is an example of how a well-established technology can be improved and used innovatively to expand its benefits.