Evaluating Aerial Systems for Crime-Scene Reconstruction

Security professionals are using ICTs as an opportunity to propose new approaches for modifying or creating innovative strategies for crime prevention and response, thus achieving greater effectiveness and efficiency. New remote sensing technology mounted on drones offers the possibility of improving crime scene reconstruction, alongside the traditional model, i.e., the physical inspection performed by an agent at the crime scene.

In order to analyse the characteristics and differences between the aerial system (drone) and the terrestrial system (laser scanning), simulations of three different outdoor scenarios envisaged in the 2021 report “Evaluating Aerial Systems for Crime-Scene Reconstruction” [1] by the National Institute of Justice were conducted at the Crisis City Training Center near Salina, Kansas: (1) an urban scene recreating a carjacking and shooting including broken glass, bullet casings and pools of blood; (2) a forest where a suicide has taken place, with empty alcohol containers and narcotics; and (3) an open field with a clandestine grave, a shovel, a cell phone and clothing.

With the results of these simulations, the differences that became apparent were, on the one hand, in favour of the aerial system (and opposed to terrestrial laser scanning): (1) it does not require forensic personnel to walk through the crime scene, risking contamination and/or destruction of evidence and bodily harm from hazardous environments; (2) it allows faster data capturing of the entire crime scene; (3) it is cheaper, costing about $15,000 (the conventional terrestrial laser comes in at about $75,000); and (4) by capturing information from above, there are no blind spots, unlike in laser scanning, where blind spots occur if there are insufficient scanning positions or obstacles.

On the other hand, laser scanning results in a higher image accuracy, with an error level of about 1 mm, and capable of preserving the quality in the dark and regardless of the environmental conditions. As far as the drone is concerned, the error level was about 1 cm and, moreover, in the case of open spaces such as the forest, the height of the drone (to avoid hitting the treetops) reduced the quality of the image. The atmospheric variables (cloud coverage, temperature, wind, precipitation…) must also be taken into account, which will condition the efficiency of the aerial system.

Therefore, when reconstructing 3D images of the (simulated) crime scene, maximum efficiency is achieved by complementing terrestrial and aerial scanning, as the combination of both systems allows faster data capturing of the entire crime scene, while maintaining a higher level of accuracy. The procedure is a non-intrusive technique that helps investigators prevent scene contamination, and the results can help officers, lawyers and judges “walk through” the scene at any time, even years later, as well as verify details such as distances and sight.

[1] Informe https://nij.ojp.gov/topics/articles/evaluating-aerial-systems-crime-scene-reconstruction


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