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P241 – Biological Factors Associated with STR Allele Detection in touch DNA samples
Touch DNA samples recovered from objects frequently produce partial or low-quality STR profiles. Understanding the biological factors influencing STR profiling success is therefore important for the interpretation of forensic touch DNA evidence.
This study investigated biological characteristics associated with STR allele detection in touch DNA samples. Cellular parameters (number of attached cells and cell size), DNA-related indicators (human DNA quantity and DNA degradation index), and keratinization-related protein markers (cytokeratin 1 [CK1] and cytokeratin 10 [CK10]) were evaluated.
Ten volunteers deposited touch samples onto four surface types (glass, polyethylene terephthalate [PET], stainless steel, and wood). Cell size was measured microscopically, DNA quantity and degradation were assessed by qPCR, and CK1 and CK10 expression levels were quantified using a Simple Western system. STR profiling was performed using the Identifiler Plus kit.
The number of attached cells differed significantly among surface materials, with higher cell counts observed on glass and wood. In contrast, cellular and DNA-related parameters showed substantial variation among volunteers. No significant differences in CK1 or CK10 expression or STR allele detection rates were observed between surface types. Spearman correlation analysis indicated that STR allele detection rates were negatively associated with cell size and DNA degradation index, and positively associated with CK1 expression.
These findings suggest that STR profiling outcomes in touch DNA samples may be associated with biological characteristics of deposited epidermal cells rather than surface type, particularly factors related to cellular morphology, DNA degradation, and keratinization status.
Authors
- Mitsuyo Machida (Department of Forensic Medicine, School of Medicine, Tokyo Women’s Medical University, Japan)
- Kazuhiko Kibayashi (Department of Forensic Medicine, School of Medicine, Tokyo Women’s Medical University, Japan)
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