I.T.@The Boulder Police Dept.
Transitioning to Digital Photography
Policies are as important as the forensics.
By David Spraggs
DIGITAL photography and image processing technology are rapidly advancing forensic investigation procedures for law enforcement agencies. At crime scenes, digital cameras and video recorders are becoming "standard issue," helping investigators record, analyze, and compare evidence. Computerized crime labs, with networked PCs, scanners, printers, and CD writers, are replacing conventional "wet" photography and darkrooms.
In court, photos and videos processed with imaging software routinely are admitted into evidence.
But the concerns, and even risks, of digital imaging must be weighed carefully against the benefits. Most agencies that embrace digital imaging also are implementing new procedures and workflows to assure the technology will be viable in court. The way an agency handles its forensic digital files is as important perhaps more important than the technology itself.
Mountains to Plains
The City of Boulder is about 26 square miles, extending from the mountains onto the Colorado plains; and contains 38,000 acres of open space.
The Boulder Police Department has about 200 commissioned members (officers, detectives, etc.) We have specialized units, including: K9, motorcycle, SWAT, school resource officers, traffic, and more. We serve a city of about 100,000 that includes the University of Colorado's Boulder campus with about 25,000 students (although the university has its own police department). FBI statistics (Uniform Crime Reporting) show Boulder's crime as consistent with other similar jurisdictions around the country. We handled more than 64,000 calls for service and investigated about 9,000 criminal complainants in 2000.
A Gradual Overhaul
During the past year and a half, the Boulder PD has brought its forensic imaging almost entirely in-house, replacing our conventional process (and much of our equipment) with a digital workflow. I was assigned the task of heading the transition because of my background in photography and crime scene investigation. The project goals as set forth by Chief Mark Beckner and the executive staff were faster turnaround time of crime scene images, more efficient evidence preparation and storage, and lower costs over time. These goals were realized by eliminating the need to outsource film development and printing.
Any image introduced into a court of law can be challenged.
The Boulder P.D. has standardized digital imaging into our crime scene investigation process. Film will continue to be used for specialized techniques (such as ultraviolet or infrared technology), but crime scene investigators and officers now carry Nikon digital cameras to every crime scene, and can provide visuals to other investigators within minutes.
Our 2- and 3- mega-pixel cameras can produce photographic quality 8x10-inch photographs, printed either on our inkjet or thermal-autochrome (Fuji Pictrography 3500) printers.
Adobe Photoshop software is used to process images, enhance them if needed, prepare them for court, and label them for storage. For each case, evidence technicians transfer the native file format digital files to a CD-ROM, and log the disc into property and evidence with accompanying documentation. The CompactFlash cards that contained the primary image files are then reused.
Guiding the entire forensic imaging workflow at Boulder Police is an updated set of policies and procedures on how to handle digital files, especially those prepared for court. We have created a path we believe other agencies can follow, and we work to share our findings with those facing the same process.
We are now looking at expanding our capabilities by purchasing a large format printer, to output displays for courtroom presentations.
We also expect to purchase more cameras (we currently have 50 in use.)
Opponents to digital imaging (as used in law enforcement) point out that software such as Adobe Photoshop makes it very easy to alter images. While this is true, many do not understand that traditional film-based images can also be altered, either in a traditional darkroom, or by digitizing negatives, then altering them. Manipulated photographs can be burned back onto film by a device called a film recorder. Technology has gone "full circle," so more than ever it is the integrity of those managing the images that enables them to stand as evidence. Any image introduced into a court of law can be challenged, not just based on the technology used to create the photograph: Is the photograph relevant? Is the photograph inflammatory?
Whether film based or digital, an image's purpose is the same: to show a reasonable and accurate representation of a crime scene, injury, etc. Also, it is important to note that an evidentiary photograph is accompanied by an officer, detective, or crime scene technician who can testify that the photograph is not misleading or incorrect. Again, the people are more important than the technology. For those people to credibly defend visual evidence, it is especially important that any agency implementing forensics digital imaging also implements a thorough standard operating procedure.
There are clear advantages to preparing images for court in a digital darkroom instead of a "wet" darkroom. In the digital darkroom, accurate, repeatable color is easier to achieve.
This is especially important when printing photos of a domestic violence or assault victim. Injuries must be represented accurately, so the severity of the injuries is neither reduced nor exaggerated.
For example, Adobe Photoshop makes it easy to remove colorcasts that would otherwise make it difficult to accurately determine the extent of the injuries.
We used Photoshop to re-examine negatives that had a green cast from poor film processing. The software enabled us to eliminate the unnatural green cast, returning the images to a more accurate representation of the crime scene.
We will often resize, adjust color balance and contrast, and sharpen an image with imaging software.
For example, sizing tools allow us to print evidence such as a footwear impression on an exact one-to-one scale. Enhancement can be done in a "wet" darkroom, but it is faster in the digital darkroom.
Batch processes can enhance a number of photographs automatically a great time saver if an entire roll of film was under- or over-exposed. Photoshop's Actions Palette allows us to track and "record" every action taken to enhance the original image; the record is printed and attached to the photograph to demonstrate each step in the enhancement and maintain the integrity of the original image.
This also allows an independent operator to reproduce exactly the photograph from the original digital file.
With well-constructed policies in place, digital technology provides investigators with new ways of capturing and examining evidence with the utmost precision.
If your agency is considering a transition to digital, discuss the planned shift with your local prosecutors, who can help you advocate for the new technology as it is introduced in court.
David Spraggs is a detective with the Boulder Police Department, handling crime scene investigation and firearm instruction.