Scientists have found a new way to discover unmarked mass graves and help find murder victims using lasers, according to a new study. In a grim but useful experiment, researchers buried several bodies in shallow graves and then used LIDAR, a surveying method that measures distance by bouncing laser light off of surfaces, to clearly detect where the graves were.
“Unmarked graves are difficult to locate once the ground surface no longer shows visible evidence of disturbance, posing significant challenges to missing person investigations,” the study, published in the journal Forensic Science International, reads. “An approach that combines LIDAR data with other established methods may improve overall results.”
To test out the LIDAR technique, researchers from the University of Tennessee and the Oak Ridge National Laboratory hand dug graves using shovels and pickaxes in a secure research field owned by the university—also known as “the body farm.”
One of the graves they left empty, as a control. They then filled the other graves with cadavers from people who had donated their bodies to science: one grave held one body, one contained three, and another had six bodies. The researchers note in the study that they took care to get the details as realistic as possible.
“Some bodies were partially clothed or bound with ligatures, and items such as bullet casings, keys, and gloves, were added during the backfilling process,” the study reads.
The researchers then filled the graves back in, stamped down the ground with their feet, and let nature take its course.
By taking multiple measurements using LIDAR, the scientists were able to create maps of the area that detected the minor changes in elevation created by the graves, and distinctly outline where they were. There was even a difference, over time, between the control grave: as the bodies decomposed, the elevation on the filled graves dropped slightly, as the dirt settled in around the body, but the empty grave didn’t settle in the same way.
“Despite considerable effort to minimize a surface mound, as in the case of this experimental study, the disturbance will still result in elevation gain, which is inevitable due to displacement resulting from burying a body in soil,” the study authors wrote. “Perhaps
it is the case that such attempts would minimize a surface mound so that it is not apparent to the unassisted observer, but this study demonstrates that LIDAR can reveal subtle differences in elevation change that might otherwise be invisible, and therefore overlooked.”
This technique could make a big difference to search parties trying to find missing persons. Our current techniques are limited and often boil down to simply scanning an area by sight, and enlisting the help of cadaver dogs. By enlisting the help of lasers, these scientists have created a simple but effective new tool for investigators.
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