According to Locard’s principle, at a crime scene traces are left by the perpetrator linking their presence to the scene, which can be crucial information for an investigator in a criminal investigation (Locard, 1930). Deoxyribonucleic acid (DNA) are left behind on items that are touched or handled even for a brief moment, and by swabbing the surface a DNA profile can be acquired (van Oorschot and Jones, 1997). Henceforth, there has been great interest in the conditions that allow primary, or direct transfer of an individual’s DNA onto an object or onto another individual (Meakin and Jamieson, 2013). There is the possibility of secondary, or indirect transfer, where the DNA of an individual is introduced into a crime scene by the perpetrator
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This led to their subsequent experiment where a group of individuals were required to exchange polypropylene tubes, which were held for a short duration with the individuals’ bare hands. van Oorschot and Jones (1997) found that the DNA profile of all the individuals who held onto the polypropylene tube were detected. Moreover, by swabbing the hands of an individual, it did not just show their DNA profile, but also the profile of others who held the same tube even when the individuals were not in contact with each other. Therefore, van Oorschot and Jones (1997) concluded that there is a possibility for secondary DNA transfer and the phenomenon will lead to the interpretation of DNA evidence becoming more complicated. With the amount of DNA recovered, it is not possible to determine whether it was transferred directly or indirectly onto an item of interest as they both show a similar order of magnitude (Meakin and Jamieson, 2013). For example, in a different study conducted by Goray et al. (2012), they illustrated that the amount of DNA recovered from secondary transfer ranges from 0-2 ng, and some of the results also fall within this range for primary transfer. The results were generated from the amount of DNA recovered on either a plastic toy or a lab coat, where an individual rubbed their hands against the toy for direct transfer, and rubbing the toy that came into contact with their hands against the lab coat for secondary transfer (Goray et al.,
This led to their subsequent experiment where a group of individuals were required to exchange polypropylene tubes, which were held for a short duration with the individuals’ bare hands. van Oorschot and Jones (1997) found that the DNA profile of all the individuals who held onto the polypropylene tube were detected. Moreover, by swabbing the hands of an individual, it did not just show their DNA profile, but also the profile of others who held the same tube even when the individuals were not in contact with each other. Therefore, van Oorschot and Jones (1997) concluded that there is a possibility for secondary DNA transfer and the phenomenon will lead to the interpretation of DNA evidence becoming more complicated. With the amount of DNA recovered, it is not possible to determine whether it was transferred directly or indirectly onto an item of interest as they both show a similar order of magnitude (Meakin and Jamieson, 2013). For example, in a different study conducted by Goray et al. (2012), they illustrated that the amount of DNA recovered from secondary transfer ranges from 0-2 ng, and some of the results also fall within this range for primary transfer. The results were generated from the amount of DNA recovered on either a plastic toy or a lab coat, where an individual rubbed their hands against the toy for direct transfer, and rubbing the toy that came into contact with their hands against the lab coat for secondary transfer (Goray et al.,