Ultraviolet Light
(Alternate Light Source)
Original Ultraviolet Light posting: September 17, 2023
Updated: March 14, 2024
The use of an alternate light source (ALS), specifically ultraviolet (UV) light with a wavelength under 490nm, should be considered as a tool during searches for human remains [2].
Recent applications during HRD searches in Virginia by Search and Rescue Tracking Institute (SARTI) members have found the use of ALS with wavelengths in the 385-395nm range to be very effective.
Collagen, an organic protein found in bone, is responsible for the fluorescent properties of animal bones. This fluorescent property degrades over time (visible for approximately 200+ years), but should be visible when viewed using light sources with wavelengths under 490nm.
According to Tzaphlidou [3], collagen represents more than 90% of the organic matrix in bone.
Forensic cases less than 50 years should benefit from the use of UV light to observe bone's fluorescent properties.
Factors that could affect a bone's fluorescent properties include heat, pH, ultraviolet radiation, and moisture.
According to a study by Gallant [1], remains that have been exposed to fire could not be differentiated from their surroundings using UV light.
Search and Rescue Tracking Institute (SARTI) began utilizing UV light technology to search for human remains on October 26, 2023 in Virginia. Searchers utilized 365nm, 385-395nm, and 390nm wavelength UV handheld ALS. This search produced successful results as searchers discovered 10 additional human bones. Since that time, SARTI has continued to deploy UV ALS with successful results on 7 searches across the Commonwealth of Virginia and continues to advance the science of ultraviolet light for the detection of human remains.
Experimentation Results Using UV Light vs. White Light at Night
White light at night
Photo showing a human femur obscured by green vegetation at night
UV Light
Photo showing the same photo as on the left, but using a UV light source
White light at night
Photo showing a whitetail deer metacarpal obscured by fallen deciduous leaves at night
UV Light
Photo showing the same photo as on the left, but using a UV light source
White light at night
Photo showing a whitetail deer mandible obscured by fallen deciduous leaves at night
UV Light
Photo showing the same photo as on the left, but using a UV light source
White light at night
Photo showing a human vertebra obscured by green vegetation at night
UV Light
Photo showing the same photo as on the left, but using a UV light source
Additional examples of animal bones when exposed to ultraviolet light
Black bear radius
Whitetail deer vertebra (C1)
Foreground: Mummified black bear paw
Background: Deer ribs
Juvenile whitetail deer mandible
Effects of Distance
Demonstration of 110-foot visibility using 385-395 nm UV ALS
Camera: Nikon D3200 DSLR
Shutter speed: 25 seconds
Aperture: f/11
ISO: 400
Focal length: 35 mm
Flash: Minolta Maxxum 4000 FA used off camera (2 full-power flashes)
ALS: uvBeast V3 385-395 nm UV held 6-feet above ground "painting" the objects
Test object: human ribs placed at 10-foot increments from the camera from 10- to 110-feet
Human Teeth
Note that the roots fluoresce more than the enamel
Left Mandibular 2nd Molar
Left Maxillary 1st Premolar
Left Maxillary 2nd Premolar
Right Maxillary 1st Incisor
Note: Unless otherwise noted, the UV light photos above were utilizing a Gearlight UV black light flashlight S100 with an ultraviolet wavelength of 390nm. #ad
References:
Gallant A. Alternate light sources in the detection of bone after an accelerated fire: a pilot study. J Forensic Sci 2013;58(S1):S221-6.
Swaraldahab, Mohamed A.H. , Christensen, Angie M. The Effect of Time on Bone Flourescence Implications for Using Alternate Light Sources to Search for Skeletal Remains. J Forensic Sci, Marck 2016, Vol. 61, No. 2.
Tzaphlidou M. Bone architecture: collagen structure and calcium/phosphorus maps. J Biol Phys. 2008 Apr;34(1-2):39-49. doi: 10.1007/s10867-008-9115-y. Epub 2008 Oct 15. PMID: 19669491; PMCID: PMC2577747.
Interesting Articles:
Could a Tree Help Find a Decaying Corpse Nearby?
Reflection of ultraviolet radiation from different skin types
Luminescence of thermally altered human skeletal remains