New drone-mounted remote sensing technologies could complement conventional ground-based laser scanning in efficiently recreating crime scenes for forensic analysis.

Evidence from a crime scene — a boot print, a tire track, a bloody glove — can give investigators the clues they need to bring persons committing crime to justice. However, conventional methods of collecting this information, including photography, charting, and terrestrial laser scanning, require forensic personnel to walk through the crime scene, risking evidence contamination as well as bodily harm from hazardous environments.

New drone-mounted sensing technologies could help investigators reconstruct crime scenes from the air without having to physically enter the space. National Institute of Justice-supported researchers from Kansas State University evaluated the use of small, unmanned aircraft systems (i.e., drones) equipped with two types of remote sensors for crime scene reconstruction and compared their performance to conventional terrestrial laser scanning.

Their findings showed that terrestrial laser scanning created more accurate images of staged outdoor crime scenes than the aerial methods. However, a combination of terrestrial and aerial scanning allowed faster data capture over the entire crime scene while maintaining a higher level of accuracy than either method on its own.

Ground-based techniques for reconstructing crime scenes require highly trained personnel to enter a scene and time — both of which increase the risk of evidence contamination and destruction — and decrease data integrity. Kurt J. Carraway and his team evaluated aerial sensing technologies as a hands-free way to collect touch- and time-sensitive evidence at crime scenes. Their study investigated the advantages and limitations of two types of aerial sensing technologies — structure from motion photogrammetry and LIDAR — and compared their performance to conventional terrestrial laser scanners from the Kansas Bureau of Investigation in crime scene reconstruction and investigation.

The methodologies for the project included:

• Terrestrial laser scanning: A trained individual strategically places several laser scanners throughout the simulated crime scene. Scans are conducted simultaneously and are stitched together to create a 3D map.
• Structure from motion photogrammetry: 2D images from a digital camera mounted on a drone are used to reconstruct a 3D model of the simulated crime scene. The drone also carries a Global Positioning System to establish control points on the ground and lights for nighttime scans.
• Light detection and ranging (LIDAR): A LIDAR system mounted on a drone records the time it takes for a laser to hit objects on the ground and reflect back to a receiver. These measurements are combined and used to reconstruct 3D images of the simulated crime scene.

To test each method's ability to assess a crime scene, the researchers worked with law enforcement partners to set up three outdoor scenarios at the Crisis City Training Center, a disaster training center for emergency response personnel near Salina, Kansas:

• An urban scene that resembled a carjacking and shooting with broken glass, bullet casings, trails and pools of fake blood, and firearms.
• A forest scene involving a suicide by hanging with pieces of clothing, empty alcohol containers, simulated narcotics paraphernalia, and rope.
• An open field with a clandestine grave with a shovel, cellphone, items of clothing — some partially buried, and restraints.

Data Collection and Study Results

Carraway and his team collected quantitative and qualitative data for each imaging method in each simulated scenario both at night and during the day.

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