Photography
Photography has many applications in forensic science. It is used in the first instance to photograph the crime scene. Then, photographs are taken of individual items of evidence, from fingerprints and bloodstains, to wounds on a victim's body both at the scene and during an autopsy. Specialized techniques such as microphotography and infrared photography can be extremely useful in particular settings. Forensic photography is a skilled job, for all photographs must be of high enough quality to be admissible as evidence in court.
A crime scene is always photographed as soon as possible, so there is a permanent record of the location in its original condition. This will probably occur after the preliminary survey of the scene when, ideally, nothing will have been touched or moved. Sometimes, however, the priority is to get emergency help for a victim and this may lead to some movement of objects. The photographer will take shots of these items in the place they have been moved to. Returning them to their original position would amount to disturbing the scene, which is bad practice. It is not possible to specify how many photographs will be taken for so much depends on the type and nature of scene. As a general guide, the forensic photographer will err on the side of caution and take too many pictures instead of too few.
Three types of photographs are taken, overall, mid-range, and close-up photographs. Overall photographs will be taken of the exterior and interior of the crime scene. Exterior photographs will show buildings and other major structures, roads, or paths to and from the scene, streets signs, and address numbers. If possible, aerial photographs will be taken because these give the broadest possible view of a crime scene in relation to its surroundings. Interior photographs are taken using the corners of the room as a guide. Overlapping views are taken, to ensure everything is covered. It is also important to take photographs of the common approach path, that is, the agreed route through which investigators enter and leave the scene of the crime. This comprises an access point and a focal point and is chosen so that there will be minimal disturbance of evidence. For instance, investigators would not choose a common approach path involving the perpetrator's possible entry point for fear of contaminating evidence at this location. A body, if there is one, is often the focal point of a common approach path. The photographer will also take shots of any possible routes taken by perpetrators or victims including entry or exit points.
Mid-range photographs will show items of evidence and any bodies in their immediate surroundings. Close-ups will focus on evidence like weapons, victims, footprints, and other evidence. A scale, such as a ruler, will give a guide to the size of the item of evidence. This is important because the photographs will later be enlarged to the appropriate size for comparison work, with shoeprints, for instance. Photos with and without this scale are generally taken. An L-shaped ruler that shows the length and breadth of the item is particularly useful. All photos taken must be recorded in a special photo log with the date, time, photographer, film, camera settings, and a brief description of what the photo shows. The settings of the camera must be such as to allow good illumination, filling in shadows with flash where needed. Flash can also be used to enhance detail or patterns. No extraneous objects such as investigators or their equipment should be seen in any of the photographs. The forensic photographer's scene of crime kit typically will include a 35-millimeter camera, normal, wide-angle, and close up lenses, an electronic flash with a cord, color and black-and-white film, scales or rulers, and a tripod. Photography is often supplemented by taking a video of the scene. But the still photographs are essential, because they are of higher resolution than a video film. The aim is to take examination quality photographs which can be studied back in the forensic laboratory in comparison with samples taken from suspects or from reference databases.
When it comes to photographing evidence that could easily be damaged or lost, such as fingerprints, shoeprints, tire tracks, and toolmarks, it is important to take the photographs as soon as possible. Fingerprints may need to be made visible, by exposing to laser or ultraviolet light, or by applying special powders before they can be photographed at the scene. Similarly, shoeprints may need treatment before they can be visualized, although those in mud or blood can usually be captured on film without special preparation. It is important to take photographs of shoeprints at a 90-degree angle to its surface and centered in the camera lens. This avoids distortion in the image and makes comparison with control shoeprints more reliable. Tire track photographs need to be taken both as part of a general scene photograph, so that their location can be precisely determined, and also close up, to determine the pattern detail on the tire so it can be identified. Photographs of toolmarks should at least show the location of this important source of evidence. However, even macrophotography may not reveal enough detail to allow the photographs to be used for laboratory comparison with suspect tools. Each item of evidence is photographed individually before being touched if at all possible, and several shots of each item are taken.
Bloodstains are found in many different locations and patterns at crime scenes. The overall photographs will show their location and distribution, which may be significant in revealing the relative positions of the victim and perpetrator. Then the photographer takes more shots close up of the individual stains that reveal the detail needed to back up pathological analysis of the injuries inflicted. Bloodstains and blood spatter patterns on the victim's body are also photographed.
It is also important to photograph any injuries on living or dead victim. A corpse is always photographed before being moved from the scene of a crime. Full body and close-ups are taken. The place where the victim lay will also be photographed again once the body has been moved and then searched for evidence. If the victim is living, the photographer will take pictures of only the minor injuries at the scene. Serious knife wounds or gunshot injuries will generally be photographed at the hospital in the interests of getting the victim medical help as soon as possible. Photography plays an important role in an autopsy, too. The body is photographed both clothed and unclothed. Frontal and profile photographs of the face and body are important, especially if there is a question of identification. Each birthmark, tattoo, scar, and any other body mark is also photographed. Photographs are taken at each stage during the autopsy process.
Photography may be an important aid to identification of a body. Photos of the face of a corpse may be simply compared with images or descriptions of missing persons. A forensic anthropologist, who is an expert in human remains, may be able to determine whether two pictures are of the same person by analyzing their bone structure. Even though two pictures may be very different in quality and in their age, similarities or differences in certain elements of bone structure may be apparent. The investigator will superimpose the two pictures, at the same image size, and compare the eyebrow area, nasal openings, and the contours of the chin.
Special illumination techniques are often used to take photographs in particular situations. Photographs taken in infrared light can sometimes help distinguish two types of ink, which look very similar in ordinary light. This may help determine whether writing has been added to an original document. Ultraviolet illumination enhances images of injuries while laser light illumination is valuable in recording fingerprints. There is also a trend towards using digital rather than conventional photography in forensics as well as in other applications. Digital images can be readily enhanced. For instance, if a fingerprint appears on an interfering background, such as a bank note, then the background can readily be removed to make the actual evidence clearer. However, it is this very ability to manipulate which makes some courts wary of digital photographic evidence.
Good quality photographs have many uses in the investigation of a crime. They can help investigators carry out a crime scene reconstruction, where the sequence of events leading up to and occurring after the actual crime is deduced. Sometimes photographs are used to help witnesses recall more about what they saw. Photographs can be faxed and widely distributed in the media or throughout a neighborhood in the search for missing persons or suspects. Judge and jury may be presented with photographs during a trial to help them understand the nature of a crime. Sometimes a photograph of an item of evidence will even be allowed to stand in for the real thing if the actual item could not be removed from the scene of crime for some reason. Photographic techniques are advancing all the time and it is the task of the forensic photographer to make best use of these to create strong, detailed images of all the evidence pertaining to a particular crime.