Getting More Detail from Crime Scene Diagrams
Written by Bob Galvin   

Although the rates of violent crimes and murders in the United States decreased in 2013, according to latest statistics provided by the FBI, most crime investigators see no slowing in the number of crime scenes they must map. The job requires a delicate balance of seasoned investigative skills, defining what evidence is most relevant, and maximizing the time available to map a scene since the evidence lasts only a short time. Many investigators have discovered that having the right technology can help them achieve their goal of solving as many cases per year as possible.

Today’s Mapping Tools Are Versatile
 
Tom Morris, a consulting crime and crash scene reconstructionist, is well acquainted with the challenges presented by crime scene documentation. Morris provides his services to the St. Louis Metropolitan Police Department Force Investigative Unit, particularly for police-involved shootings. The unit relies on Morris’s skills to examine forensic evidence they have collected. For Morris, documenting crime scenes can be more challenging than crash scenes because the location of evidence and difficulty in capturing it differs greatly between the two types of scenes. Traffic accidents are usually confined to a roadway. But in crime incidents, activities may occur inside buildings or other locations.
 
The total station has been a mainstay for all kinds of scene mapping because of its effectiveness at reading slope distances from a particular point and measuring angles. Most modern total stations measure angles via electro-optical scanning of extremely precise digital barcodes etched on rotating glass cylinders or discs within the instrument. Photogrammetry—the science of making measurements from photographs—is another method used often. Morris uses both total stations and photogrammetry for his scenes. Photogrammetry is especially helpful because, Morris said, “If we need to look at a case from the last year or longer, we still have the ability to take the photos captured at the scene and recover information from it using them.”
 

A hypothetical scene showing a drive-by shooting. This scene is a still-frame from a 3D animation created with a diagramming software program. For an actual crime scene like this one, the scene might have been mapped with a total station, then the data would be downloaded to the diagramming software to build the 3D animation.
 
3D Scanning Usage Expands
 
For his “toolbox,” Morris uses total stations, software for 3D/close-range photo modeling, and forensic CAD software for producing accurate and detailed scene diagrams for use in court. In the last few years, Morris has been using a robotic total station that allows the operator to control the instrument from a distance via remote control. This eliminates the need for an assistant staff member since the operator holds the reflector and controls the total station from the observed point.
 
Laser scanning is another extremely valuable tool because of its efficiency, time savings, and ability to collect vast amounts of evidence points at nearly any type of scene. The St. Louis Metropolitan Police Department is working toward acquiring a laser scanner to experience these very benefits.
 
Time savings is as important as gathering sufficient evidence when mapping crime scenes, Morris noted. “I can use the other tools effectively, but it takes time,” he said. “This limits the number of cases I can complete per year. With equipment like the scanner, where we can document 30 or 40 million points in a short timeframe and work inside the point cloud, we can apply this technology on more cases,” Morris said.
 
The ability to collect more information from a scene in less time than with other measurement tools and the ability to capture and preserve the scene as-is are additional benefits to using laser scanning. What’s more, Morris said, “You can do an analysis on that crime scene while you’re no longer at the scene.”
 

A 3D view of a vehicle collision in front of a house. In the collision, a pedestrian was struck. This scene was created with a combination of photogrammetry to model the house, and total station data to capture the roadway and surrounding environment. These two data sources were then combined in the diagramming software to build a 3D presentation.
 

A photo of the house and street where a pedestrian was hit by one of two cards involved in a collision. The photo was used to create the 3D model inside of photogrammetry software for export to a drawing program.
 
Building 3D Perspectives Is Goal
 
The biggest differentiator with using a laser scanner is its ability to capture a 3D perspective of a scene with complete evidence details. This is a big value for the investigator since scanned crime scenes often are used in courtroom presentations. Data from a laser scanner can be imported into CAD software, Morris explained, where users can leverage advanced CAD commands and tools in the software to work within a 3D environment.
 
“It’s being able to look at the scene from different perspectives,” said Morris. “A lot of drawing programs only give you a top-down look, so you’re looking overhead and in a 2D perspective. With CAD software, for example, I can rotate that environment around and look at it from any perspective that I need to while I’m actually completing the model of a building or the position of a vehicle.”
 
The software also allows Morris to modify symbols such as a car or streetlight to the exact car or light that was in the scene he has mapped. “This allows me to more accurately represent scene details instead of just using representative symbols,” Morris said.
 
Preplanning
 
Detective David DeLeeuw with the Ocean County (New Jersey) Sheriff’s Office is another advocate of laser scanning. The sheriff’s office acquired a laser scanner in 2009, becoming the first law enforcement agency in New Jersey to purchase a laser scanner. The scanner is so versatile that investigators use it for a variety of scenes including suspicious deaths, motor vehicle accidents, and shootings. DeLeeuw uses the scanner mostly for serious crimes such as aggravated assaults and homicides.
 
Interestingly, the detective noted that scanning is equally helpful for preplanning responses in structures that might become part of crime scenes later on. These include public buildings such as schools, courthouses, government offices. “These are all sites of interest that might be potential targets,” DeLeeuw noted.
 
Real-time View of Scanned Data Guides Investigators
 
Like Morris (the St. Louis crime scene reconstructionist), DeLeeuw values the unique capabilities of scanning. For example, one manufacturer’s laser scanners typically are coupled with point-cloud processing software. Because DeLeeuw operates a scanner from that particular manufacturer, he sets the parameters on his laptop where the software is loaded so that scanning can be accomplished. Scene data is imported automatically into the software as the scanner covers the scene. As a result, “I’m actually seeing the point cloud populate,” the detective said.
 
A special benefit of this process, DeLeeuw said, is that as he is looking at the evidence data captured, “If I’ve missed something, I can go back and scan it.” Also, if there is an obstruction in front of the scene, the user can simply pick up the scanner and move it around or behind the obstacle.
 
Newer scanner models now have an on-board operating system that allows the user to enter parameters, then view scanned data in real time through an LCD screen. The scanner also can be operated remotely through a smartphone, tablet, or laptop, according to DeLeeuw. “This means the operator does not have to be in the scene to operate the newer scanners, but can operate them remotely,” he said. Likewise, newer software has much tighter integration with the point-cloud database and streamlined diagramming tools.
 
Video Adds Another Dimension to Scene Documentation
 
With the ubiquitous influence of smartphone technology and its capability for capturing video of any situation, video now factors into crime scene documentation as well. Video footage can provide multiple perspectives of a crime scene, which can be useful for helping to build a 3D environment. But Morris offers a cautionary note. “We can say we’ve seen a video and think we know exactly what happened,” he said. “But if I show this video’s information to you in a different perspective, you may think it didn’t happen that way at all.”
 
Therefore, Morris believes the most important benefit of video is the information that appears in still-frames. “We want to know what landmarks are visible,” Morris said. “Then I can go out with a total station and identify those landmarks that were inside of a photograph or a still-frame video, then use photogrammetry to capture the spatial information of the objects I can see in the video. This means the photogrammetry software used with the total station can produce enough evidentiary data to feed into the forensic CAD drawing software to create a detailed 3D presentation of the scene.
 
3D Crime Scene Presentations Gain More Court Acceptance
 
The drawing software plays a key role in building the 3D representation of the crime scene, Morris said. However, he does not refer to diagrams he creates as scaled diagrams. Instead, “we refer to them as diagrams that have scaled qualities,” he said. “You’re creating a 3D environment that you can use to get the right information from it to do the analysis that will help you understand better what has occurred (at the crime or crash scene),” Morris added. “Sometimes the location of a line or pavement seam is important, but the width is not. Therefore, not everything in the drawing is to scale, although the spatial relationships between the evidence items are.”
 
As scanning technology and other crime scene mapping tools have advanced during the past 15 years, the ability to present a finished diagram of a crime scene in court (whether it is 2D or 3D) has been increasingly successful. The use of 3D technology with tools such as laser scanning to build what amounts to a virtual walk-through of a crime scene has been particularly well received. The Leica ScanStation is the only laser scanner that has received a federal Daubert ruling stating that data from the scanner is admissible as scientific evidence. In a recent precedent-setting case in California (Bertoli v. City of Sebastopol et al.), the judge admitted into scientific evidence both the Leica ScanStation scan data and all of the expert analyses built upon it. The data and analyses included a 3D working model, a shadow study, and hundreds of exhibits, all of which was provided to the jury for their deliberation.
 
Morris concurs with the positive experiences that laser scanning has so far demonstrated. “We’re not taking a gamble with it,” Morris argued. “There has been a general acceptance of this kind of evidence in most courts in the country.”

About the Author
 
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it is a freelance writer who covers topics related to law enforcement and the technology of crime- and crash-scene reconstruction. His office is located in Oregon City, Ore.

 

 
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