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An Alternative Method of Photographing (The following paper appeared as a Technical Report in the “Afterwords” section of the Mar/Apr 1994 issue of the Journal of Forensic Identification)
by SCOTT R. SPJUT Introduction There are several techniques which can be utilized to photographically document developed latent prints on clear plastic material. Some of these techniques require the utilization of lasers or monochromatic light sources. Although often times superior, these methods may be difficult for the technician who does not have access to such a light source. Comparable results can be obtained after cyanoacrylate ester development, without the use of a forensic light source. The use of a shadow box and an incandescent light can produce photographically legible latent prints on plastic material after development with cyanoacrylate ester. The shadow box can easily be constructed from an ordinary cardboard box that is lined with black paper. The black paper acts as the shadow area of the box. The latent prints photographed with this method are often equal in quality to those developed using fluorescent dyes and a forensic light. Procedure Preparation The box used for this demonstration is open--ended with the dimensions 12" x 8" x 10". A 5" x 2" opening is cut on one of the side panels and black paper is placed within the box, opposite to that opening. The incandescent light is placed at the open end of the box, with the newly cut opening facing upwards. Procedure The plastic material which has previously been processed with cyanoacrylate is placed on top of the cut opening. The incandescent light is placed through the open end of the box, to allow the light to illuminate up through the cut opening. The visible latent prints are viewed through the cut opening, and are photographed accordingly. The use of a camera copy stand is useful to stabilize the box and camera. Occasionally the plastic material will be creased or otherwise wrinkled, making clear photography difficult. By placing the processed plastic in an embroidery hoop and pulling it tightly, many wrinkles can be greatly decreased. Embroidery hoops can be purchased at most craft retailers. The incandescent light can be adjusted to vary the desired lighting and contrast depending on the visibility of the latent prints to be photographed. Conclusion This technique can be used to photograph most types of clear plastic materials including polyurethane wrap, plastic sandwich bags, cellophane, and latent prints on clear adhesive tape. Latent prints on the sticky side of tape are especially simple to photograph prior to cyanoacrylate fuming. If required, the tape can be gently placed on clear glass, sticky side down. The glass is then turned upside down to photograph the latent prints in correct position. Although not a replacement for dye stained latent prints, this technique can provide adequate results when photographing latent prints on clear plastic. The costs are minimal, and the preserved latent prints can easily be used for comparisons to suspect prints or for automated fingerprint systems. For further information contact:
Scott R. Spjut
(Editor --— A modification of the technique above is also a useful technique
for fluorescent photography of the latent prints on plastic bags and other
transparent or translucent materials. The illumination technique for fluorescent
photography is modified to an angled frontal illumination of the evidence
instead of rear illumination. The interior of this box or a darkened background
will absorb stray and reflective light which can reduce overall contrast.
This article was reprinted in “THE PRINT” 10(4), April 1994, pp 1-2 |