Forensic analysis of trace DNA

Abstract

This research investigates the potential of DNA typing of epithelial cellular material recovered from objects that have been touched by individuals. Trace DNA analysis is a relatively new field in forensic science and as yet, little has been published regarding the best methods available. After an investigation into the most successful techniques for DNA recovery, extraction, and amplification, the most favourable methods for successive analysis of samples were chosen. Optimal methods chosen were the use of swabbing for the recovery of cellular material, an organic DNA extraction method with an ethanol precipitation step, quantitation using the ACESTM Human DNA Quantitation System, and amplification using AmpliTaq® Gold DNA polymerase. Using these methods DNA was successfully extracted and typed using the CTT STR triplex from objects including shoe insoles, car steering wheels and gear sticks, bed sheets, and from the surface of the skin touched by another individual. DNA mixtures were recovered from shoes and cars after two different simulated theft scenarios. Of the samples that yielded DNA, some did not give full or partial CTT profiles after amplification. The likelihood of obtaining a full CTT profile after amplification depended on the amount of cellular material deposited, which was shown to vary greatly from person to person. Objects touched by individuals were shown to be a suitable matrix for the analysis of DNA for forensic use.