A trace of evidence

New material aids investigators in lifting trace evidence


     When examining fingerprints in blood, the blood must be dry and the fingerprint dusted with magnetic powder before applying the casting material. If the substance is applied when the blood is wet, it will destroy the fingerprint and smear the blood on the surface. When attempting to lift latent fingerprints from human skin, it is recommended that the application occur within 2 hours. Standard dusting with magnetic powder produces identifiable results with the AccuTrans transparent application. However, photography with back light is necessary to eliminate the need to reverse the latent print. Drying time was approximately 3 minutes at 78 degrees. (Figure 4 and 4A on Page 87 show latents lifted from human skin.)

     In the toolmarks test, brown AccuTrans was used to recover several tool impressions in wood. The tool impressions were produced with a flat-head screwdriver and a framer's hammer with a check design on the hammer's face. The screw driver and the hammer produced good quality impressions, and brown AccuTrans did a superb job in capturing these toolmarks from the wood; the impressions showed excellent detail and did not need to be reversed. Drying time was approximately 3 minutes at 78 degrees F.

     Applying material to the Smith & Wesson 9mm handgun barrel was extremely easy; after adding a plug at the chamber portion of the barrel, a slight amount of a release agent, such as gun oil, was applied and then the barrel was filled with AccuTrans brown. Simply pulling on the impression released the cast from the barrel. The results proved to be of excellent quality with the chamber, lands and grooves clearly visible. The product's drying time was approximately 5 minutes at 78 degrees F.

Pro and cons

     On the positive side, researchers found AccuTrans easy to use and durable. They noted the material had very little or no shrinkage at various temperatures and produced high quality latent fingerprint and toolmark impressions. In addition, they found the product has no smell and does not stain. They reported that the dispenser gun was easy to operate (once loading is achieved and the cartridge locked into place, attachment of the tips is keyed and a spreader tip is available for even distribution of the polyvinylsiloxane material in a 1-inch wide path for latent fingerprints). On the negative side, brown AccuTrans had visible voids, cracks and air bubbles when applied for casting, which can require the investigator to perform multiple castings. This was the only negative researchers encountered with the product.

     Overall, researchers found two primary benefits to AccuTrans use: ease of mixing and ease of application. The accuracy of detail and available colors also weigh heavily in its favor. They concluded AccuTrans is so precise it can capture the ink depth of a dollar bill, making it a logical choice for forensic investigators.

     M. Dawn Watkins is a senior latent print examiner/crime scene investigator at the Palm Beach Gardens (Florida) Police Department. King Brown is the crime scene supervisor with the West Palm Beach (Florida) Police Department.

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