A system could aid forensic searches and crime-scene mapping by detecting reflections from human...
Volunteers sometimes spend months trudging through remote terrain to search for lost hikers or crime victims.
A new tool could soon pinpoint forensic evidence from the sky instead. By identifying how traces of blood and other human signs reflect light when found on various natural surfaces, the scientists say searchers will be able to quickly scour large areas for clues about missing persons-dead or alive-using images acquired by drones.
Mark Krekeler, a mineralogist at Miami University in Ohio, and his colleagues realized that the same approach, supported by the right spectral data library, could potentially detect forensic evidence.
To build their tool, the researchers measured how human-related features, including blood, sweaty clothing and skin tones, reflect different wavelengths of light.
Previous studies have examined such reflective "Signatures" to identify blood, "But the signature depends on the surface itself and may change over time," Krekeler says.
He and his team analyzed thousands of samples, such as bloodstains on different rock types, recording how they changed as the blood dried.
The researchers customized software that mixes the known reflective signatures of various surfaces to reproduce a target of interest.
Rock and clothing signatures can be combined to seek a hiker lost in the mountains, or a blood signature can be mixed with those of clothing and sand to search for a wounded person in a desert.
It can distinguish between an animal and a human in dense forest, search a cityscape for evidence of a specific person in a blue cotton dress, or determine whether soil is stained by blood or diesel fuel, Krekeler says.
Developing best-practice protocols for search teams could make such technology routine for investigations and forensics, Krekeler says.