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Limitations in photography are twofold: limitation of the camera in general and lack of experience or training of the photographer.
Cameras cannot produce the same view that the human eye sees; it is the photographer’s use of the camera settings that can affect what can or cannot be seen in a photograph. A trained photographer will recognize difficult lighting situations and adjust the camera settings accordingly. Often, more than one photo will be taken of the same view, in order to properly expose for widely varying conditions in a single view.
The use of digital cameras allows a crime scene photographer to instantly review their photos and make changes to the camera settings if needed to capture the best possible image while still on the scene. Critical thinking skills and analysis are constantly applied during the scene documentation process. An inexperienced photographer will often forgo the review process, relying on their camera to “make the right decisions” for settings.
To ensure the most accurate capture, processing and analysis of crime scene photographs, the management of criminal justice agencies and forensic laboratories puts in place policies and procedures that govern facilities and equipment, methods and procedures, and personnel qualifications and training. These Standard Operating Procedures (SOPs) are intended to maintain and demonstrate the integrity of the images and information captured at a crime scene and its admissibility in court. Crime scene photography SOPs ensure uniform processes are used by photographers and the information represented in the images accurately represents objects and conditions at the scene as they are found.
The Scientific Working Group on Imaging Technology (SWGIT) works to set quality guidelines for the capture, storage, processing, analysis, transmission, output and archiving of images. These guidelines provide good general practice standards for crime scene photographers and other individuals performing photography within the criminal justice system. SWGIT guidelines are available.
Is there anything else about crime scene photography that would be important to the non-scientist, or any common misconceptions regarding this topic?
A common misconception is that digital images can be changed more easily than film prints and done to mislead the court. Photographs created in a darkroom from film can also be altered by a skilled photographer using a wide variety of techniques, so they are not necessarily more accurate than digital images. While digital software exists that can make drastic changes to a digital image, a comparison of the altered image with the original makes any changes obvious. This is why proper chain-of-custody procedure and workflow is necessary.
According to the SWGIT guidelines: “Documenting image enhancement steps should be sufficient to permit a comparably trained person to understand the steps taken, the techniques used, and to extract comparable information from the image.”
Similar to scientific research being documented to allow other scientists to perform the same steps and get the same results, image enhancement documentation should be specific and in order. The SWGIT guidelines include examples of documentation and draft SOPs (PDF download) for agencies to customize.
Another misconception may be reinforced by television crime dramas, and that is the idea that every crime scene unit and/or investigator has high-end camera equipment and is thoroughly trained in crime scene photography. Though many are, it should be clarified that equipment, training and procedures vary widely among agencies.