Goray Mariya, Hartog Mike, Monkman Heidi
College of Science and Engineering, Flinders University, Bedford Park, South Australia, Australia.
College of Science and Engineering, Flinders University, Bedford Park, South Australia, Australia; University Van Hall Larenstein, Leeuwarden, Netherlands.
Sci Justice. 2024 Nov;64(6):585-598. doi: 10.1016/j.scijus.2024.09.002. Epub 2024 Sep 8.
Touch DNA is one of the most common types of biological material collected during criminal investigations. Diamond™ Nucleic Acid Dye (DD) has been shown to aid in touch sample visualisation and target sampling. It has also been used as a method of shedder categorisation that is cheaper and quicker than DNA methods. However, the DD method routinely involves manual cell counting, which can result in intra and inter-person variability similar to other manual techniques used in forensic science, for example, fingerprint identification. Additionally, DD based shedder categorisation involves counting cells in a portion of the touch deposit to extrapolate an individual's shedder status, and the sampling effect of such estimations is currently unknown. The present study tested different data analysis aspects of the DD method, including counting variability within and between people, shedder classification differences based on different counting methods (entire thumbprint, sub-section of a print with most cells, sub-section of a print deemed most representative of the entire thumbprint, and random sections), the use of ImageJ software to semi-automate counting and the use and extension of the DD method for investigating DNA Transfer, Persistence, Prevalence and Recovery (DNA-TPPR). The results of this study show that there are meaningful differences observed during counting processes both between and within people. These differences tended to increase as the factor of time, or the duration of counting, rather than the complexity of cell deposits being assessed. Investment in cell counting software that eliminates personal factors, such as boredom fatigue, can remedy most of these issues, however, will require optimisation, such as fibre recognition. Shedder testing was shown to be affected by the choice of sampling and categorisation methods, and suggested that using an entire finger or larger section size can provide increased precision. Finally, inverted worn gloves stained with DD may provide an acceptable alternative for hands in DNA-TPPR investigations, providing an interesting alternative for future research.
接触性DNA是刑事调查中收集的最常见生物材料类型之一。钻石™核酸染料（DD）已被证明有助于接触样本的可视化和目标采样。它还被用作一种比DNA方法更便宜、更快的脱落细胞分类方法。然而，DD方法通常涉及手动细胞计数，这可能会导致与法医学中使用的其他手动技术（例如指纹识别）类似的人际和个体差异。此外，基于DD的脱落细胞分类涉及对接触沉积物的一部分中的细胞进行计数，以推断个体的脱落细胞状态，而这种估计的采样效果目前尚不清楚。本研究测试了DD方法的不同数据分析方面，包括人与人之间和人内部的计数变异性、基于不同计数方法（整个指纹、细胞最多的指纹子部分、被认为最能代表整个指纹的指纹子部分以及随机部分）的脱落细胞分类差异、使用ImageJ软件进行半自动计数以及将DD方法用于研究DNA转移、持久性、流行率和回收率（DNA-TPPR）。这项研究的结果表明，在计数过程中，人与人之间以及人内部都观察到了有意义的差异。这些差异往往随着时间因素或计数持续时间的增加而增加，而不是随着被评估的细胞沉积物的复杂性增加而增加。投资消除个人因素（如厌倦疲劳）的细胞计数软件可以解决这些问题中的大部分，然而，这将需要优化，例如纤维识别。脱落细胞测试显示受采样和分类方法选择的影响，并表明使用整个手指或更大的部分大小可以提高精度。最后，用DD染色的倒置磨损手套可能为DNA-TPPR调查中的手部提供一种可接受的替代方案，为未来的研究提供了一个有趣的选择。
