Assessing the effectiveness of alternate light sources in the search for skeletal remains.

Many search and recovery operations for human skeletal remains are unsuccessful due to difficulties recognizing bones in outdoor environments even when evidence indicates the last known whereabouts of missing individuals. Though the collagen component of bone is known to emit fluorescence, this property has not been leveraged consistently during skeletal remains searches. Thirty-six mock searches were completed in 5000 ft zones of eastern deciduous forest by volunteers associated with the Virginia Department of Emergency Management. Pig and deer bones were scattered and partially concealed under brush and leaf cover. Pairs of volunteers were allowed up to 1 h to conduct searches in their usual pattern. Nighttime searches were conducted with handheld alternate light source (ALS) devices (uvBeast™, Crime-lite, ForenScope, and Labino AB), which produced ultraviolet (385-395 nm), violet (395-425 nm), blue (455 nm), cyan (510 nm), or green (~530 nm) lights. Filtered safety glasses were paired with appropriate ALS. Daytime searches were conducted under the same parameters, without ALS. Results indicated that (1) nighttime searches with ALS produced a recovery rate more than triple that of daytime searches (p < 0.0001) and that they were often completed more quickly, and (2) the violet Crime-lite, due to breadth of illumination and strength of fluorescent response, consistently produced the highest recovery rate (95%). Data suggest that nighttime searches with ALS can be used both as the primary search method for locating and recovering human skeletal remains, and as a secondary method for recovering any bones expected to be present but not found during daylight searches.