Ultraviolet Light

(Alternate Light Source)

Original Ultraviolet Light posting: September 17, 2023

Updated: November 13, 2023

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].


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.


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.


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. 


The Commonwealth of Virginia Search and Rescue began utilizing UV light technology to search for human remains on October 26, 2023 in Tazewell, Virginia (VDEM Mission #2023-10-27-4195). Searchers utilized 365nm, 385-395nm, and 390nm wavelength UV handheld flashlights. This search produced successful results as searchers discovered human long bones, human hand bones, a human hyoid bone, and human bone fragments.


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

Photo using iPhone 12 flash

5-feet from human ulna

Photo using UV flashlight

5-feet from human ulna

Photo using iPhone 12 flash

10-feet from human ulna

Photo using UV flashlight

10-feet from human ulna

Photo using iPhone 12 flash

15-feet from human ulna

Photo using UV flashlight

15-feet from human ulna

Photo using iPhone 12 flash

20-feet from human ulna

Photo using UV flashlight

20-feet from human ulna

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: the UV light photos above were utilizing a Gearlight UV black light flashlight S100 with an ultraviolet wavelength of 390nm. #ad

References:


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

Light: It's secrets revealed