Reference Citation: An earlier version of this paper was published as Schiro G. Collection and Preservation of Evidence. In: Muth AS, editor. Forensic Medicine Sourcebook. Detroit: Omnigraphics, 1999; 45-59.
George Schiro, MS, F-ABC
EXAMINATION AND DOCUMENTATION OF THE CRIME SCENE
Before the investigators begin examining the scene of the crime, they should gather as much information as possible about the scene. Once again, a slow and methodical approach is recommended. Information is gathered to prevent destruction of valuable and/or fragile evidence such as shoeprints, trace evidence, etc. Once all of the information is gathered, a mental plan is formulated as to how the crime scene will be analyzed. Copious notes and relevant times should be kept on every aspect of the crime scene investigation. The examination of the scene will usually begin with a walk through of the area along the "trail" of the crime. The trail is the area where all apparent actions associated with the crime took place. The trail is usually marked by the presence of physical evidence. This may include the point of entry, the location of the crime, areas where a suspect may have cleaned up, and the point of exit. In some cases, a walk through may become secondary if potential evidence is in danger of being destroyed. In that case, this evidence should be preserved, or documented and collected as quickly as possible.
The purpose of the walk through is to note the location of potential evidence and to mentally outline how the scene will be examined. The walk through begins as close to the point of entry as possible. The first place the investigators should examine is the ground on which they are about to tread. If any evidence is observed, then a marker should be placed at the location as a warning to others not to step on the item of interest.
A good technique to use indoors on hard floors is the oblique lighting technique (also known as side lighting). A good flashlight with a strong concentrated beam is the only tool needed. The room should be darkened as much as possible. If a light switch which a suspect may have touched needs to be turned off, then make sure the switch has been dusted for fingerprints first. Do not close any blinds or shades until after all general photographs have been taken. In the side lighting technique, a flashlight is held about one inch from the floor. The beam is then angled so that it just sweeps over the floor surface and is almost parallel to the surface. The light is then fanned back and forth. Any evidence, such as trace evidence and shoeprints, will show up dramatically. Under normal lighting conditions, this evidence may be barely visible or completely invisible.
As the walk through progresses, the investigators should make sure their hands are occupied by carrying notebooks, flashlights, pens, etc., or by keeping them in their pockets. This is to prevent depositing of unwanted fingerprints at the scene. As a final note on the walk through, the investigators should examine whatever is over their heads (ceiling, tree branches, etc.). These areas may yield such valuable evidence as blood spatters and bullet holes. Once the walk through is completed, the scene should be documented with videotape, photographs, and/or sketches.
If available, a video camera is the first step to documenting a crime scene. Video can provide a perspective on the crime scene layout that cannot be as easily perceived in photographs and sketches. It is a more natural viewing medium to which people can readily relate, especially in demonstrating the structure of the crime scene and how the evidence relates to the crime. The video camera should have a fully charged battery as well as date and time video display functions. A title generator and "shake free" operations are also nice options. If a title generator is not available, then about 15 seconds at the beginning of the video should be left blank. This will allow the addition of a title card with any pertinent information to the beginning of the crime scene video. The condition of the scene should remain unaltered with the exception of markers placed by the investigators and any lights turned on during the walk through. These alterations can be noted on the audio portion of the video. Before recording, the camera range should be cleared of all personnel. Any people in the area should be forewarned that recording is about to commence and they should remain silent for the duration of the video. This prevents recording any potentially embarrassing statements.
Once the video camera begins recording, it should not be stopped until recording is complete. The key to good video documentation is slow camera movement. A person can never move too slowly when recording, yet it is all too easy to move the camera fast without realizing it. This is why video is not ideal for viewing detail. People have a tendency to pan past objects in a manner that does not allow the camera to properly capture the objectís details. This is why slow panning of an area is necessary and it should be panned twice in order to prevent unnecessary rewinding of the video when viewing.
The video should begin with a general overview of the scene and surrounding area. Recording should continue throughout the crime scene using wide angle, close up, and even macro (extreme close up) shots to demonstrate the layout of the evidence and its relevance to the crime scene. If recording in a residence, the camera can show how the pertinent rooms are laid out in relation to each other and how they can be accessed. This is sometimes lost in photographs and sketches. After recording is complete, it is wise to leave about 15 seconds of blank media to prevent the crime scene video from running into anything else previously recorded on the media. The video should then be transferred to high quality master media. The master media should be protected from accidental erasure after transferring the crime scene video and the master should be stored in a safe place. Copies can then be made from the master media.
Whether a video camera is available or not, it is absolutely essential that still photographic images be taken to document the crime scene. If a video camera is available, then photography will be the second step in recording the crime scene. If video is not available, then still photography will be the first step. Photographs can demonstrate the same type of things that the videotape does, but photographs from the crime scene can also be used for direct comparisons. For example, natural size photographs (sometimes referred to as one-to-one photos) can be used to compare fingerprints and shoeprints photographed at the crime scene to known fingerprints or shoes from a suspect. This is the main advantage of photographs over video.
Almost any type of camera with interchangeable lenses and a digital format of four or more megapixels or, for film, a format of 35mm or larger will do in crime scene photography. The lenses should include a 28mm wide angle lens, a normal 50mm lens, and a lens with macro capabilities (1:4 or better). The flash unit used with the camera should be one that is not fixed to the camera. It should be able to function at various angles and distances from the camera. This is to allow lighting of certain areas to provide maximum contrast, place the flash in hard to reach areas, and reduce flash wash out which can render the item photographed invisible. If not using a digital format, print and/or slide color film (25-200 ISO) should be used. A tripod, a level, and a small ruler should also be available for one-to-one photography. It may be of help to the investigation to have a Polaroid camera or a portable digital printer handy for instant photographs. For example, an instant photograph of a shoeprint found at a crime scene can be provided to investigators who are running a search warrant on a suspect's residence. The photo will tell them the type of shoe for which they are searching.
The photography of the crime scene should begin with wide angle photos of the crime scene and surrounding areas. When shooting the general overall scene, the photos should show the layout of the crime scene and the overall spatial relationships of the various pieces of evidence to each other. A good technique to use indoors is to shoot from all four corners of a room to show its overall arrangement. The next set of photos should be medium range to show the relationships of individual pieces of evidence to other pieces of evidence or structures in the crime scene. Finally, close up photos should be taken of key pieces of evidence. A ruler should be photographed with items where relative size is important or on items that need to have natural sized comparison photographs. The object should first be photographed as is, then photographed with the ruler. It is important that when doing natural size photography that the ruler is on the same plane as the object being photographed and the CCD or film plane is parallel to the ruler. This is why a level and a tripod are necessary. Notes should also be taken as to what the investigator is photographing or wishes to demonstrate in each photograph. This is to prevent the investigator from getting the picture back at a later date and trying to figure out what he or she was trying to accomplish with the photo. The same areas should be photographed in the same sequence as mentioned above in the paragraphs on videotaping.
The final phase in documenting the scene is making a crime scene sketch. The drawback of photographs is that they are two-dimensional representations of three-dimensional objects. As a result, most photographs can distort the spatial relationships of the photographed objects causing items to appear closer together or farther apart than they actually are. If spatial relationships of the evidence are important or if something needs to have proportional measurements included in it for calculations (such as bullet trajectory angles, accident reconstructions, etc.) then a sketch must be made of the crime scene.
A sketch is usually made of the scene as if one is looking straight down (overhead sketch) or straight ahead (elevation sketch) at a crime scene. A rough sketch at the scene is usually made first on graph paper in pencil with so many squares representing so many square feet or inches. Directionality of the overhead view is determined by using a compass. Using a tape measure or other measuring devices, measurements are taken at a crime scene of the distances between objects and/or structures at the crime scene. These measurements are proportionally reduced on the rough sketch and the objects are drawn in. Two measurements taken at right angles to each other or from two reference points will usually suffice in placing the objects where they belong in a sketch. Double measurements should also be taken to make sure they are correct. This is especially true where calculations will later be used. A final sketch can be made later using inks, paper, and ruler, or a computer. The original rough sketch should be retained and preserved in case it is needed at a later date. Once the scene has been thoroughly documented then the evidence collection can commence.
RECOMMENDED READING: Moreau, Dale M. Fundamental Principles and Theory of Crime Scene Photography. Quantico: Forensic Science Training Unit, FBI Academy.
Redsicker, David R. The Practical Methodology of Forensic Photography. Elsevier: New York, 1991.
Sketching Crime Scenes. U.S. Dept. of Justice, FBI.