Forensics Journal - Stevenson University 2011

STEVENSON UNIVERSITY The Evaluation of Upconversion Powders Using an Infrared Laser for Latent Fingerprint Visualization In Comparison to Conventionally Utilized Fingerprint Powders Marisa Bender INTRODUCTION MATERIALS AND METHODS The ultimate goals for the fingerprint examiner are to successfully develop or enhance prints that are not normally visible (latent) and to identify or eliminate questioned exemplars based upon the original fingerprint. Because the latent fingerprint is invisible to the naked eye, it becomes necessary to find the means to differentiate it from the surface on which the fingerprint is found. Examiners must develop the fingerprint, thus turning it into a colored product that can stand out for detection. The utilization of optical, physical, physio-chemical, and chemical methods can help achieve this goal [1]. Materials The superglue INSTAbond S-100 (lot #GG-074) used in the superglue chamber was obtained from ACCRAbond Inc. The black fingerprint powder (Carbon black, CAS#1333-86-4) and white fingerprint powder (Titanium dioxide CAS#13463-67-7, zinc stearate CAS#557-05-1) were obtained from Lightning Powder Co., Inc. and applied with a fiber glass “zephyr” style brush. The magnetic black powder used was also from Lightning Powder Co., Inc. and applied with a magnetic brush (Sirchie Fingerprint Laboratories, Inc.). White magnetic powder (iron powder CAS#7439-89-6, titanium dioxide CAS#13463-67-7) from Lightning Powder Co., Inc. was used for added contrast on specific substrates. The green fluorescent powder (Greenwop) was obtained from Lightning Powder Co., Inc. and applied with a “zephyr” style brush. The upconversion fingerprint powder under the trade name “VISAS Green” was supplied by BVDA International. A squirrel hair brush was utilized to apply this powder. The use of fingerprint powders in casework and at crime scenes is one of the most effective and convenient methods of detection. There are many types of fingerprint powders that can used based upon their ability to provide contrast for the substrate on which the fingerprint was found [2, 3]. The most commonly utilized powders include regular flake metal powder, magnetic powder, and fluorescent powder. The flake metal powder is considered to be the most sensitive on smooth nonporous surfaces. The stearic acid component in the powder helps it adhere to the ridges of the deposited fingerprint [1, 4]. Magnetic powders have

Forensics Journal - Stevenson University 2011 | Page 56