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Analysis of Fingerprint Samples, Testing Various Conditions, for Forensic DNA Identification

NCJ Number
Date Published
January 2017
6 pages
This project performed extensive analysis to better understand the challenges for DNA typing from fingerprint samples, with the goal of developing valuable profiles (approximately 50-percent complete).
Fingerprints can be of tremendous value for forensic biology, since they can be collected from a wide variety of evidence types, such as handles of weapons, tools collected in criminal cases, and objects with no apparent staining. DNA obtained from fingerprints varies greatly in quality and quantity, which ultimately affects the quality of the resulting STR profiles. Additional difficulties can arise when fingerprint samples show mixed STR profiles due to handling by multiple persons. The current project first applied a tested protocol for fingerprint sample collection (swabbing with 5-percent Triton X-100). DNA extraction was then performed using an enzyme that works at elevated temperatures, and PCR amplification was conducted with AmpFlSTR® Identifiler® using 31 cycles. The impact of time on deposited fingerprints was investigated, revealing that although the quality of profiles deteriorated, full STR profiles could still be obtained from samples after 40 days of storage at room temperature. By comparing the STR profiles from fingerprints of the dominant versus the non-dominant hand, the study found a slightly better quality from the non-dominant hand, which was not always significant. Substrates seem to have greater effects on fingerprints. Tests were conducted on glass, plastic, paper, metal (US quarter dollar, made of Cu and Ni), and common substrates in offices and homes. Best results were found for glass, followed by plastic and paper. Almost no profiles were obtained from a quarter dollar. Important for forensic casework, the project also assessed three-person mixtures of touched fingerprint samples. Unlike routinely used approaches for sampling evidence, the surface of an object (bottle) was sectioned into six equal parts, and separate samples were taken from each section. The samples were processed separately for DNA extraction and STR amplification. The results included a few single source profiles and distinguishable two-person mixtures. On average, this approach led to two profiles approximately 50-percent complete per touched object. Some STR profiles were obtained more than once, thereby increasing the confidence. (Publisher abstract modified)
Date Published: January 1, 2017