Publication: Comparative efficiency between different swab types for touch dna recovery from different surfaces
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Date
2025
Authors
Sirajudin, Alya Amirah
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Abstract
Deoxyribonucleic acid (DNA) analysis is a fundamental tool in forensic science, enabling human identification in criminal investigations. In cases where visible biological evidence such as blood or saliva is absent, touch DNA has emerged as an alternative source of genetic material. However, touch DNA presents significant analytical challenges due to its low quantity, variable transfer, and inconsistent recovery from different surfaces. This study focused on evaluating the efficiency of different swab types and surface materials in the recovery and amplification of touch DNA to improve its forensic applicability. Touch DNA samples were deposited through natural handling to simulate realistic forensic scenarios. Three swab types (cotton, dacron, and nylon-flocked) were used to collect samples from glass, ceramic, and plastic surfaces. DNA extraction was performed using a silica-based method optimized for low-template samples. Quantitative polymerase chain reaction (qPCR) analysis revealed low and variable DNA yields across all swab–surface combinations, with no statistically significant differences observed between swab types. To assess amplification feasibility, polymerase chain reaction (PCR) targeting mitochondrial DNA (mtDNA) regions of 176 bp and 310 bp was conducted. Agarose gel electrophoresis demonstrated a markedly higher amplification success for the 176 bp mtDNA fragment compared to the 310 bp fragment across all conditions. Surface type did not show a consistent effect on amplification outcomes. These findings indicate that amplicon size is a critical determinant of successful touch DNA analysis. The use of short mtDNA targets enhances amplification reliability, supporting the forensic utility of touch DNA in cases involving low-template biological evidence.
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