The transfer of cellular material from one surface or individual to another through innocent human contact can have serious implications in forensic reporting. DNA transfer has previously been demonstrated to be influenced by many factors including age and sex of the individual, in addition to the nature of the objects handled. However, there has been little investigation into the relationship between DNA transfer and the ethnicity of the contributor.

To investigate variation in DNA transfer quantities among four different ethnicities, a total of 16 female volunteers - four from each ethnicity; African, South Asian, Levantine and Arabian Gulf were recruited. Participants were asked to wash their hands with a standardised soap for 1 min and resume daily activities for 1 hour, after which they were asked to handle a knife for 1 min under at maximum strength.

A total of 88 DNA samples were collected and extracted using Chelex-100, with each participant sampled in four replicates, followed by quantification using the Quantifiler Trio™ system (Applied Biosystems, USA), amplification using the GlobalFiler™ IQC PCR kit (Applied Biosystems, USA), followed by capillary electrophoresis on the SeqStudio® (Applied Biosystems, USA), and analyzed using the GeneMapper® ID-X software.

DNA concentrations were analyzed using GraphPad Prism®. Analysis of variance revealed significant differences in DNA transfer quantities among the different ethnic groups (p = 0.0002), with Levantines having the highest (mean = 0.036 ng/µl) and South Asian participants exhibiting the lowest DNA transfer quantities (mean = 0.0038 ng/µl), which corresponded with differences in STR profile completeness. Variation between individuals from the same ethnic group (intra-ethnic variation) showed no significant difference.

The results showed that a substantial proportion of the profiles (43%) were classified as inconclusive mixtures, whilst the major contributor was identified in 27% of the total profiles. Notably, in one instance, the major contributor’s profile did not belong to any of the participants.

Our findings suggest that differences in DNA transfer were observed between donor groups classified by ethnicity; however, these findings should be interpreted with caution as DNA transfer is influenced by multiple biological and environmental factors. Importantly, transferred DNA could constitute the major component in a mixed profile, leading to serious implications in forensic reporting and the process of due justice.

Authors

• Bushra Idris (American University of Ras Al Khaimah, United Arab Emirates)
• Maheen Hussain (American University of Ras Al Khaimah, United Arab Emirates)
• Maryam Alnaqbi (American University of Ras Al Khaimah, United Arab Emirates)
• Alreem Alsuwaidi (American University of Ras Al Khaimah, United Arab Emirates)