Shooting Incident Documentation with 3D Laser Scanners
Written by Noreen Charlton   

This article appears in the July-August 2021 issue of Evidence Technology Magazine.
You can view that full issue here.

AS THE NUMBER OF SHOOTING INCIDENTS continues to rise in the United States, proper documentation of these scenes becomes more imperative. In addition, the public is demanding more transparency in the aftermath of officer-involved shootings, which adds an additional level of the need for accuracy, thoroughness, and compelling visual presentations.

3D laser scanning is a process in which a laser captures real-world information, used in the digital world for scene documentation and analysis, to create an exact measurable copy of even the most complex scenes. Photographs have a tremendous amount of value, but they rarely have the same impact as a three-dimensional representation of a scene. Laser scans allow the viewer to visualize the scene in much more detail, providing a complete documentation tool, as it will document everything within its line of sight. In turn, the location is forever preserved digitally for review and analysis.

When a scene is captured in a precise, detailed, photo-realistic 3D view, the investigator creates the foundation for virtual storytelling. The scanner eliminates potential human error within measurements. There are no more fixed perspectives or overlapping photographs to achieve a similar view of an officer, witness, or suspect. Scan data provides an aspect of relational space that assists investigators in locating evidence and forensically reconstructing the circumstances of the incident.

Preparing to Scan

Before scanning a shooting scene, the bullet holes should be labeled. Typically, this is accomplished by way of identifying different bullet series. For example, if a bullet entered the exterior wall of a residence and perforated through the interior side of the wall, those bullet holes could be labeled A1 and A2, respectively. These markings ensure that the final trajectory report, produced with software, is consistent with the photographic documentation of the scene.


Arrow labels are used to mark different bullet paths. Then, trajectory rods, with Koppa spheres, are inserted into the entry hole of the bullet path.

Next, the investigator must insert trajectory rods into the bullet holes, keeping in mind shooting reconstruction basics. If necessary, centering cones will assist with stabilizing the rod in larger or irregular holes.

While not required, it is suggested that you use trajectory spheres for measurement repeatability. When trajectory rods are scanned without spheres (Liscio, Guryn, & Stoewner 2017), the software user must choose points on the trajectory rod to obtain measurements. These points may differ between users and can introduce small discrepancies between measurements from one user to the next.

However, the addition of spheres eliminates measurement discrepancies, and provides repeatability within the project. Lightweight spheres, affixed to the trajectory rod, ensure that the angle measurements reported in the software are the same every time, regardless of the software user. Repeatability is an essential factor for courtroom testimony and consistency with results.

Documentation with a 3D Laser Scanner

Given that a 3D laser scanner is a line-of-sight device, you may need to move the scanner into multiple positions to capture all of the trajectory rods. If necessary, the investigator can scan trajectory rods and move them to a secondary location in order to not have several prepared at once. When the scanner documents something in a scene, it is forever preserved in its original location. Where photography can be difficult in tight spaces, a handheld laser scanner offers the freedom to scan in some of the most hard-to-reach environments.

Scanner settings can vary, but the use of trajectory spheres will provide the ability to scan from a farther distance and a lower resolution, thus saving time on scene. As bullets begin to perforate different objects and surfaces, they can begin to tumble or deflect. For this reason, you should only scan the trajectory rod for the first entry of a bullet path. The software will allow you to virtually illustrate that bullet through the scene on the same path. This tool helps determine whether something or someone may have been struck by a bullet when comparing it to additional holes or defects on the scene.

Analysis in 3D Software

Forensic analysis software allows the investigator to conduct shooting reconstruction with scan data captured at the scene. The software can remove guesswork or potential human error associated with hand measurements, and also provides visual presentations that cannot be achieved from two-dimensional photographs.


Scanned project point cloud with trajectory rods in one brand’s 3D software. The addition of virtual protractors provides a visual representation of the reported measurement.

Once the scan data is imported into the software, the user can either select the trajectory rods or spheres to begin the analysis process. Once selected, the user will then adjust the impact plane to the surface that was impacted by the bullet.

The software reports the azimuth (horizontal) and inclination (vertical) angles in several angle conventions, and provides the ability to add virtual protractors for visualization of the measurements.

Once a trajectory has been determined, the software provides the ability to virtually extend the cone/rod to determine the approximate shooter location. Further, an investigator can choose to continue the bullet path through the scene, which helps determine a potential termination location of a bullet.

Upon completion of analysis within the software, a report can be generated for each trajectory to include its position within the scene and associated measurements.

Visual Presentations

For years, law enforcement has had to face the CSI Effect as it pertains to courtroom testimony. Now, more than ever, there is a sense of urgency for an agency to be as transparent as possible after officer-involved incidents.


A screenshot of shooting incident reconstruction on a vehicle in 3D software. The software provides the ability to change the color of the virtual trajectory rods and cones and label them with evidence placards.

Diagrams, forensic animations, virtual reality, and fly-through videos are some of the many presentations that can be created with 3D laser scan data. They provide the fulfillment for that desired “CSI Effect”, allowing the public to see more and feel as though they have a more complete understanding of the events that transpired.

Perspectives are key in a shooting incident. While photography is certainly beneficial, it does not provide the spatial relationships that can be obtained with 3D laser scanning. Scan data can assist in confirming or refuting a statement made about the incident as it provides complete 360° views with all the elements of the original environment. These perspectives can be visualized by way of screenshots, fly-through videos, or panoramic images.

The scan project of an exterior shooting scene is frequently supplemented with a satellite image. This provides the investigator the ability to present the shooting over long distances which were not captured by a laser scanner. This imagery, along with 3D modeling, can be used to present a scene in a more comprehensive way than ever before.


About the Author

Noreen Charlton is a FARO Field Application Engineer and former Sr. Crime Scene Analyst with the Las Vegas Metropolitan Police in Las Vegas, Nevada, where she worked for more than a decade. Throughout her time in the field, she responded to nearly 4,000 scenes, including more than 100 homicide investigations, 30 officer-involved shooting (OIS) scenes, and multiple scenes throughout the 2017 Las Vegas mass shooting investigation. Charlton has testified as an expert witness in both state and federal courts in the state of Nevada. She is a current member of the Crime Scene Investigation Consensus Body of the American Academy of Forensic Sciences Standards Board (ASB).


References

Liscio, E., Guryn, H., & Stoewner, D. 2017. Accuracy and Repeatability of Trajectory Rod Measurement Using Laser Scanners. Journal of Forensic Sciences, 63(5), 1506–1515. https://doi.org/10.1111/1556-4029.13719

 
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