Think of a crime scene as being like a kaleidoscope. Similar to twisting the end, with the kaleidoscope's array of mirrors and colored shapes, the slightest alteration to a fresh crime scene can give an entirely different look and reality to it.
Therefore, it's important to capture and preserve details of the crime scene as early as possible while they are untainted.
Various digital imaging technologies have evolved over the past few years that can image a crime scene within a short time frame. And notably, the inexpensive technologies aiding crime scene investigations are gaining acceptance in courtrooms.
Keep in mind that these technologies are not a cure-all for capturing and explaining the many details and complex circumstances of a crime scene. Digital imaging is, in most cases, a supplemental technique to crime scene data gathering, which may also include photography, photogrammetry, videotaping, crime scene mapping (as with a total station, for example) and diagramming.
3D scanning and panoramas
The term "digital imaging" tends to be used as a catch-all phrase to describe both 3D laser scanners and panoramic cameras. But these are two different technologies.
A panoramic camera records high-resolution photography and can record measurements with photogrammetry software. A 3D laser scanner, on the other hand, creates both a panoramic photograph and then automatically records millions of highly accurate measurements. It's like a total station on steroids, and everything within the scanner's field of view is measured.
One example of today's panoramic camera offerings is the Panoscan MK-3, which is a third-generation panoramic camera. It can photograph a full 360-degree image in less than one minute, even in low-light scenes. Images generated by the MK-3 can be presented as flat panoramic images, or as movies in most virtual reality players such as QuickTime VR, Flash VR or JAVA-based players.
Forensic crime scene photography and tactical mapping are among the most recent applications in which the MK-System is used.
Panoscan seems ideal for crime scene mapping because users can capture an entire room with one image, whereas if users photograph a room using a DSLR (digital, single, lens, reflex) camera, you might need to take, say, 300 photos to capture that same room to show to a jury.
"With one scan, you can basically create a virtual crime scene," says Don Schmalzbauer, a forensic crime scene investigator who owns and operates Forensic Reconstruction Services in Minneapolis. Due to Panoscan's high-resolution imaging, the user can zoom in and out on a particular object, or any other detail, within the captured image (what the device's maker calls a "hot spot") compared with video, where you have to zoom in on a specific object, then zoom back out.
"It actually is still a digital photo," Schmalzbauer, a Panoscan user, says, describing what the device creates. "Depending on your resolution and your settings, the image could be up to an average of 240 vertical line pixels in a second versus a shutter speed (using a regular digital camera) of 240th of a second," Schmalzbauer adds. A regular DSLR camera is rated at 8 to 15 megapixels, he continues. "Panoscan can shoot an image up to 600 megapixels."
Point clouds
The adoption of 3D laser scanning within police agencies is driven by the need to quickly photograph and measure the scene. The Leica Geosystems ScanStation 2 3-D laser scanner (pictured on Page 68 capturing the site of the JFK assassination in Dallas, Texas) allows a user to first generate a 360-degree panoramic photo of the scene, then it generates up to 50,000 highly accurate measurements per second (the raw data is called a "point cloud") of everything within its field of view.
Long after the scene has been processed and released, a user can return to the crime scene and make measurements between any two points in the point cloud. Detectives can also determine what a witness could have seen from any viewpoint.
The ScanStation can be used indoors or out, in complete darkness or bright sunshine. It can measure up to 900 feet, and because of its range and versatility, the California Highway Patrol, which uses six of the scanners, reports it can open roadways up to 50-percent faster after major collisions.
Details are in the diagram
Static displays of crime scenes are used most often in court presentations. However, depending on the digital imaging vendor's product used, these displays must usually be supported with other data.
Therefore, diagramming software such as Crime Zone Version 8, a program from The CAD Zone Inc., is essential for creating a 3D diagram of the crime scene using measurements taken with a total station, a photogrammetry program, or some other mapping device.
"With nearly all of the digital scene capture methods, the … program can use digital photos right in the diagram," explains Janice White, CAD Zone president. Crime Zone not only imports measurement data from other digital sources, but it can import satellite photos, evidence photos, and even superimpose a building's front exterior in 3D view, White says.
Measurements always vital
No matter what digital imaging technology is used, the crime scene data measurements are at the core of showing the events that most likely occurred. That's certainly the consensus at the Force Investigation Division of the Los Angeles Police Department in California. The division, which uses Panoscan, does not investigate but rather captures the crime scene.
The unit uses its digital imaging equipment to supplement a Crime Zone diagram made from measurements of a crime scene generated by a total station.
"The measurements [are] the most critical thing," Sgt. Barbara Barrist emphasizes. "We're able to take a 2D diagram showing a house or a large facility within the diagramming software, click to a specific room, and show a Panoscan movie. This is really helpful for attorneys going to court."
Modeling to scale
Another crime scene mapping solution to consider is the DeltaSphere-3000 system from 3rdTech. According to 3rdTech, the DeltaSphere product combines 3D laser scanning with high-resolution digital photographs to produce photo-realistic 3D computer graphics models.
"When a [DeltaSphere] user is done, he has a to-scale, color computer graphic model of a crime scene that can be studied from any viewpoint," explains Doug Schiff, 3rdTech's vice president of marketing and business development. "Our SceneVision-3D software ... can produce diagrams, 3D computer graphics models, and panoramic images," Schiff explains. "You can add lines to show bullet or blood trajectories.
"And we are reading total station data into SceneVision," he says, adding that soon a total station function will be part of the product.
SceneVision can also add close-up photos with a digital camera as high-resolution insets directly into the 3D model.
If you need to capture a large, sprawling crime scene, SceneVision is "not a very long-range scanner," Schiff notes. "If the scene will extend for a few blocks or past many houses, that's when you might want to combine SceneVision with total station data since most total stations will shoot long distances."
Cost justified
The cost for digital imaging systems is pricey, with some systems starting at around $40,000 to $50,000; and depending on the product purchased, it could rise to as much as $200,000. Is the technology worth the price tags? Apparently, selected law enforcement agencies think so. But it also depends on the amount of crime scene investigation required for a particular agency.
The Los Angeles Police Department's Barrist reports a positive experience with digital imaging technology using a Panoscan device. She says scanning resolution is high and that she can accomplish four scans in as little as 30 minutes.
Since there is always pressure to clear a crime scene quickly, Barrist says Panoscan helps do that well. "I can clear a crime scene for a 2- to 3-minute imaging, then move to another view for an additional 2-minute imaging," she says. She notes that it is more difficult to clear a scene requiring more than 20 minutes for just one laser imaging; such scenes require more than one imaging.
Focus on schools
The uses of digital imaging are varied, ranging from scanning crime scenes to creating virtual tours of scene exteriors and interiors, to tactical planning for public buildings.
Schools, which today have become a major target for active shooting incidents, are well suited to digital imaging scanning device applications. In fact, offers Minnesota forensic expert Schmalzbauer, there are so-called "safe school" programs whereby school administrators work closely with local police departments to develop a protocol in case of a critical incident. If a police department has a digital imaging device, it can document the layout of a school's buildings.
"Usually, if you have a major shooting incident, you're going to have more departments (or first responders) coming in to assist, and they may not know the layout of the school, or [have] never been inside," Schmalzbauer explains. "To be able to look at [the layout of buildings] in a preliminary way gives these responders a big advantage."
Image alterations a concern
When law enforcement agencies first learned of thermal imaging technology, they were hesitant to adopt it right away, reasoning that courts may not accept the scanned image (a still photo).
A big part of this fear rested in the belief that a digital image that had been scanned could be altered or manipulated.
However, many forensic groups reject this notion. Among them is the Scientific Working Group on Imaging Technology (SWGIT), one of several sub-groups of the Mendota Heights, Minn.-based International Association for Identification. On its Web site, SWGIT offers a litany of "myths" about the use of digital imaging for crime scene investigations along with responses that debunk them.
SWGIT challenges the myth that scanned digital images are easy prey for manipulation by retorting there are methods to prove a digital file's integrity, and that experts may be able to determine whether a digital image, film photography, or film negative has been altered.
Schmalzbauer argues that digital imaging technology yields a credible representation of a crime scene's details. "It's a high-resolution digital image," he says. "As long as you testify that it's a true and accurate representation of the scene you scanned, it's like anything else you would testify to based on evidence documented with a regular camera."
Bob Galvin is a freelance writer based in Oregon City, Ore.
