Crime Scene Photographs
Footwear impressions can be located in and outside the crime scene. Remember, the suspect had to arrive and depart the scene. The location that will later be photographed in detail should be photographed showing the general crime scene and surrounding areas. When photographing the scene always remember to take overall, medium and close up shots before you begin your comparison photographs. Always use a relationship technique when relating footwear evidence to the crime scene or to other items of evidence. An easy way to do this is to place a numbered marker next to the evidence print and photograph. Make sure the crime scene photographs have been taken prior to altering the evidence with numbered markers. When making quality examination photographs of the evidence prints, be sure to use the same number you used when you were showing relationship. After this has been done, quality examination photographs can then begin. In order for a footwear examiner to perform a quality examination, high-quality, close-up photographs are required.
This can be easily obtained with a little time and patience. The camera is mounted on a tripod and rotated in such a manner that the plane of the film is parallel to the plane of the print. This will enable the darkroom technician to print a 1 to 1 scale photograph of the impression for comparison. The print, the scale and an information card should fill the frame of the film. When using a flash, the flash should be held at least at a 45 degree angle from the print and fired from three different positions with at least 100 degrees separation. By using this oblique lighting procedure a different amount of light can be reflected from the shadowed and non-shadowed areas providing greater contrast.
This oblique lighting will cause a greater amount of contrast, and detail can be obtained in the photograph. The best way to do that is to fire the flash off at the three different positions of the tripod making sure not to get the legs of the tripod in the way of the flash. A minimum of four photographs are taken for each footprint, one without a scale and three with the scale. A minimum of three photographs are taken for each footprint when not using a flash, one without a scale and two with the scale. The scale should always be placed parallel to the side of the shoe, never in the print itself.
When at all possible, photographs should be taken of prints made by each foot. While there is a minimum number of photographs suggested, there is NO maximum. It is always better to have too many, than too few. Remember to take overall, medium and close-up photographs prior to altering the impressions with a scale.
When the impressions are photographed correctly, they often proved the footwear examiner with a more detailed impressions that lifting or casting thus resulting in a more definite examination and comparison.
In tracking, which is the process of following the footprints of an individual, photograph the scene as you found it and then lace numbers next to each impression. Photograph the scene showing the impressions’ numbers, this way you can come back later and relate where each impression was found. Then the quality examination photographs can be taken.
Casting an Impression
In the past years, plaster of paris was used for the casting of footwear and tire read impressions; however, it is now recommended that only dental stone be used for casting impressions. Dental stone, like plaster of paris, is a form of gypsum, but provides a superior result. Dental stone has proven to be much stronger, and therefore, does not require that reinforcement material be placed in the cast during the pouring. Most importantly, dental stone is more durable and harder than plaster of paris and can be cleaned in the laboratory with a potassium sulfate solution, with virtually no loss or erosion of detail from the surface. Dental stone is available from local dental supply stores and the overall cost is less than plaster of paris.
Three dimensional impressions should always be cast if there is clarity and the surface will permit.
- The cast gives lifelike and actual-size molding of the original impression including uneven surfaces and depths.
- The cast gives reproduction of microscopic characteristics.
- In deep impressions, the cast gives reproduction of characteristics of the side of outsoles and midsoles of the shoe which usually are not reproduced in photographs.
- Focus or scale problems are eliminated.
- Provides tangible 3-dimensional evidence.
- Backs-up the photographs.
How Many Impressions do I Cast?
The way to answer this question is simple. If at a crime scene you develop 10 latent impressions, you might surmise that some of these impressions have sufficient detail to effect an identification and others may not. Would you still lift five of those ten and leave the other five at the scene? Remember the real possibility that the most valuable evidence might be left behind. Use the same consideration when casting or photographing footwear impression evidence.
Evidence left at the crime scene can never be recovered and will follow you all the way to court.