Written by Noreen Charlton
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
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.
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.
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
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.
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.
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).
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