The Mega-Pixel Revolution Arrives
by David Spraggs, Police Magazine
(Reprinted with permission from Police Magazine.)
The implementation of new technology is a double-edged sword; forensic digital imaging is no exception. Digital imaging has distinct advantages that can be realized by most law enforcement agencies; but it has disadvantages and, potentially, risks as well. The question is: Do the benefits outweigh the disadvantages?
A year and a half ago the Boulder, Colo. Police Department -- under the guidance of Chief Mark Beckner and executive staff -- agreed that digital photography could provide clear benefits to the department. I was assigned the task of transitioning the department to digital imaging because of my background in photography and crime scene investigation. After a lot of research, training, testing and questions, the Boulder Police Department is successfully using digital imaging. Film is not dead, however. Simply put, film cameras can do things that digital cameras cannot. Specialized techniques such as infrared and ultraviolet photography cannot be done with digital cameras.
Regarding image quality, today’s two and three megapixel cameras can print a photographic quality 8"x10" reflective print. Printer technology has also progressed rapidly. An inexpensive inkjet printer can print nearly continuous tone prints. Digital imaging technology is progressing as rapidly as computer technology.
For example, the new $5,500 Nikon D1x is a six megapixel camera. Two years ago a camera with this resolution cost $30,000. Don’t be afraid to take the plunge; digital cameras that will serve your agency well today will still provide high quality images years from now, even though the camera may be considered outdated.
Advantages and Disadvantages
The advantages of digital photography will vary depending upon the agency using the technology. The Boulder Police Department has about two hundred commissioned members. We have not supported a wet darkroom for many years. Because we had to out-source film processing and printing, the advantages of keeping all imaging in-house is clear. Faster turnaround time and lower cost are two benefits. It can be argued that the chain of custody is actually stronger because the weakest link -- sending the film to a private lab -- is eliminated.
The initial cost associated with implementing digital photography can be high. However, the memory cards, which replace film, can be reused thousands of times, eliminating the need to purchase film. The cost of out-sourcing film processing and printing is expensive, especially when a case requires hundreds of 8"x10" prints. Our lab charges ten dollars per print. Depending on the printer, your agency can expect to pay anywhere from fifty cents to two dollars and fifty cents per 8"x10" -- a significant savings, although the personnel costs must be factored into the equation as well.
As a detective, the speed of digital imaging is a great advantage. For example, I was paged out in the middle of the night to investigate a sex assault that occurred in a remote part of the city. A crime scene investigator responded and photographed the scene with a digital camera. When I got back to the office a few hours later, the photographs were on my desk. This allowed me to explain the scene to other investigators. It was a complex crime scene and the details would have been difficult to convey without the aid of photographs.
One of the great advantages of using a digital camera at a crime scene is that the photographs can be reviewed on the camera’s integral viewing screen. Proper exposure, focus and composition can be immediately confirmed, reducing the number of poor crime scene photographs. Most digital cameras that are acceptable for forensic work have a video output. One person can enter a crime scene and take digital photographs. The camera can be hooked up to a television and all involved personnel can view detailed color images of the scene. This is great for limiting access to crime scenes.
Most digital cameras record information about each photograph, such as date and time, specific camera settings, etc. This information is contained in a text file that is associated with the image until the image file is changed or renamed, depending upon the camera manufacturer. It is possible to archive images on a recordable compact disc (CD Rom or CD-R), open them years later and know the exact date and time that the photograph was taken.
While digital imaging has many positive attributes, it also has its downside. New technology and equipment mean additional training. Evidence technicians and/or photo technicians need to learn new hardware and software.
Digital cameras also mean new workflow issues. Previously, an officer or crime scene investigator had a never-ending supply of film at their disposal. With digital photography the memory cards are reused. Film costs are reduced or eliminated, but personnel now have additional tasks and more equipment to keep track of. Of course, the biggest potential problem is digital images in court.
Digital Images in the Courtroom
The first question that arises when discussing forensic digital imaging is, “Aren’t digital photographs easy to manipulate?” The answer is yes. In fact, digital photographs are very easy to alter. It does not take a lot of skill to create a believable fabricated photograph. Traditional photographs can also be manipulated in a “wet” darkroom; however, it is faster and easier to alter digital images.
With the advent of hardware such as film scanners and film recorders, the credibility of all photographs can be questioned, not just digital photographs. Digital imaging technology has progressed to the point where it is possible to create film from a digital image file. A device called a film recorder accepts digital data -- such as a TIFF or JPEG file -- and creates either color negative film or color transparencies from the digital file; film is no longer “safe” because new film can be created from altered digital files.
What conclusions can be drawn from this? The technology exists to manipulate an image whether it was captured by a digital camera or film camera. This is important because the authenticity of film-based images can be questioned by an astute defense attorney as well, not just images captured digitally.
So what can we do about this? Remember that photographs are usually introduced into court as demonstrative evidence, to provide a visual representation of the scene that will aid the jury in understanding the crime, but which has no effect on the question of guilt. Both digital photographs and conventional photographs should be a true and accurate representation of a crime scene. Digital photos only differ in the technology used to create the reflective image. I believe that the technology used to create the reflective image is not as important as the credibility of the witness testifying to the photograph.
It is up to the prosecutor and witness testifying on the stand to convince a judge or magistrate that the photographs presented are accurate and reasonable. The judge considers relevance and authentication when deciding whether to allow photographs into court proceedings. Testifying that a written policy was followed will go a long way toward establishing authentication.
Before an agency decides to implement digital imaging, it is recommended that you contact your local prosecutors and let them know about your planned transition to digital. Confirm that they are prepared to support the new technology if it is challenged in court. Education and communication go a long way toward making sure all agencies involved are on the same page.
Guidelines for Standard Operating Procedure
Every agency using digital imaging technology should have a detailed procedure articulating exactly how the images are to be handled. The procedure should not be limiting. Allow for growth and technological advances, but make sure that every area a defense attorney can attack is covered. There are many ways to properly implement digital technology; the following information is provided as an example of what works well for the Boulder Police Department.
Digital cameras store the digital files in standard file formats. The most common are JPEG and TIFF. Each file format has advantages and disadvantages. The JPEG file format offers distinct advantages. Because the file size is reduced, many more pictures can fit on the memory card and it takes much less time to “write” the image to the memory card. TIFF files offer higher image quality in absolute terms. But, only a few images can fit on the memory cards and it takes from thirty seconds to a minute to “write” one picture to the memory card. However, stay away from the camera’s low quality setting which corresponds to high JPEG compression ratios. It’s tempting to use this setting because the memory card can hold hundreds of images, but the image quality suffers. Boulder PD captures images in a low compression JPEG format. This offers the best balance of high image quality and moderate file sizes. For example, a 64MB memory card can hold forty low compression JPEG images from a Nikon Coolpix 990 -- about the same as a roll of film.
Chain of Evidence
The CompactFlash cards should only contain images from one incident or crime. As with film, most agencies wouldn’t photograph two crime scenes on one roll of film. It is important to note that the digital image files are the evidentiary item, not the memory card itself; this allows the “evidence” to be transferred to archival storage and the memory card to be reused. Digital cameras allow the user to selectively delete images. Obviously, this cannot be done with film. Our policy specifies that images cannot be deleted from the CompactFlash cards. It’s just “cleaner” in court to articulate that no photographs were deleted while at the crime scene.
After an officer logs the CompactFlash cards into property and evidence (just like with film), an evidence technician transfers the digital files to a CD-R. Boulder PD policy is to create a CD-R only on the computer in our digital imaging lab, because we run regular system diagnostics on this computer to confirm that it is working properly. The images are burned onto a CD-R before they are opened in any software program. Essentially, we “drag and drop” the digital images onto the CD, before the files are ever opened.
Once the CD-R is created, before the images are erased off the CompactFlash card, the digital images are opened on the CD-R to confirm that the transfer was successful. At this point the images are erased off of the CompactFlash card and the card is returned to the appropriate crime scene investigator.
Only one case is placed on a CD-R, which is not a problem because the cost of CD-Rs is very low; we pay under fifty cents per disc. A log is kept of the date and time that each CD-R is created. We also record the serial number of each CD-R. This allows the department to prove that the CD-R archived in property and evidence is the original and contains the original digital images. This prevents accusations of tampering.
After the CD-R is archived in property and evidence, if an investigator or prosecutor requests copies we create a contact sheet with six pictures per sheet. All of our image enhancement is done in the digital imaging lab and only authorized users are allowed access to the computer there.
Every photograph printed for court has documentation regarding the enhancements made to the image. Techniques such as contrast adjustments, lightening and darkening, dodging and burning, sharpening, and color balance are just a few of the enhancements possible with Photoshop. If image enhancement is needed, a copy of the original digital file is created; this is defined as the working file. The working file is enhanced and the original disc is kept in property and evidence.
Adobe Photoshop allows the user to record exact changes made to an image by using the Actions Palette. The Actions Palette can be printed and attached to the image. So if a defense attorney questions an image, you can provide the attorney with a copy of the original data file and the Actions Palette. This allows an enhanced image to be exactly reproduced. In fact, it is easier to print identical images in a digital darkroom than it is in a conventional darkroom.
Implementation of New Technology
A gradual transition to digital imaging will allow your agency to develop policies and procedures that work well for your specific needs. After our digital imaging lab was complete, the first digital cameras were issued to detectives and evidence technicians. A few months later, fifteen Nikon Coolpix 990 kits were issued to crime scene investigators.
This was the “beta testing” phase of the project. Is the equipment working well? Did we issue enough CompactFlash cards with each camera? Are the evidence technicians capable of handling the new workload? Many other questions arose and were answered during this phase.
The final phase is to issue about thirty point-and-shoot two-megapixel cameras to patrol. Currently, all patrol officers carry a point-and-shoot 35mm camera and a Polaroid camera. These two cameras will no longer be in service once the digital cameras are on line.
Of course, training is necessary to successfully integrate any new technology. Selected members of Boulder PD completed excellent training classes taught by Jack Jacobia of The Institute for Forensic Imaging (www.engr.iupui.edu/ifi). Many other training classes are available. A few of the trainers I am aware of include: George Reis of Imaging Forensics who is very well known and offers great classes (www.imagingforensics.com); and Ed Williams, who is also a respected law enforcement digital imaging trainer (www.id-bureau.com).
Conclusion
Digital imaging can offer increased speed and efficiency. Although the initial monetary investment can be high, it is possible to realize long-term cost savings with a well implemented program. Smaller agencies can now keep all imaging in-house, tightening the chain of evidence. Digital cameras offer certain advantages, but film cameras will continue to be an important component of forensic imaging.
The fact that digital photography is rapidly being incorporated by law enforcement agencies is indisputable. The next few years will be very important in securing digital imaging as an accepted technology. My hope is that all police agencies using this technology will do so in a thoughtful, careful manner to ensure that defense attorneys cannot successfully challenge digital photographs in court.
David Spraggs is a detective with the Boulder, Colo. Police Department. In addition to his duties as a firearms instructor and a crime scene investigator Dave teaches forensic photography and crime scene investigation.
This article is reprinted with permission from Police Magazine, online at www.PoliceMag.com.
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