Abstract:
DNA analysis has become a prominent intelligence tool in identifying violent criminals
in the criminal justice system. Touch DNA is the type of trace evidence found at crime
scenes. The donor causes the transfer of the epithelial skin cells by physical contact
with other objects, which leaves a trace amount of DNA on surfaces. In this study,
cutting out and swabbing methods for sampling trace DNA evidence have been selected.
This study was carried out to (a) determine the most effective and accurate ways for
sampling the touch DNA evidence and (b) to analyze the success of DNA profiles of
different types of touch evidence. The protocol was followed in two ways; the first way
was a statistical evaluation of the success of DNA profiles of different types of criminal
touch evidence categories analyzed for 2019, 2020, and 2021 years. The percentage of
success of positive DNA profiles obtained for food, garment, cigarette buds, slippers,
handles of knives, swabs of nails, and other items, was 60%, 80%, 92.59%, 20%, 53.5%,
33.34%, and 44.45%, respectively. Cigarette/“beedi” buds have represented a higher
percentage of success in DNA profiles. The second attempt was to identify a better
substrate for obtaining the maximum amount of DNA among selected items such as
matches, fabric material, and chewing gums. This study proved that fabric material was
the best substrate for obtaining the maximum amount of DNA. Then the researchers
tried to select a better sampling method for fabric material to obtain the maximum
DNA amount. According to quantification results, the cutting out method was the best
sampling method out of the two sampling methods of cutting out and swabbing for
fabric material. The study evaluated two different sampling techniques to obtain DNA
from touch substrate, proving that the sampling method depends on the types of the
substrates of touch evidence.
