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."
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.