Forensic Science Program, Division of Health and Applied Sciences, Faculty of Science, Prince of Songkla University, 15 Kanjanavanich Road, Songkhla, 90110, Hat Yai, Thailand.
Forensic Science Innovation and Service Center, Prince of Songkla University, 15 Kanjanavanich Road, Songkhla, 90110, Hat Yai, Thailand.
Int J Legal Med. 2022 Sep;136(5):1237-1245. doi: 10.1007/s00414-022-02858-2. Epub 2022 Jun 17.
Bloodstains on fabrics may be washed or cleaned to eliminate incriminating evidence. These actions reduce the chances of obtaining an interpretable DNA profile. Previous studies have shown that conventional short-tandem repeat (STR) typing is affected by various factors associated with washing or laundering of stains. Here, we aim to increase the chances of obtaining interpretable STR profiles from laundered bloodstains using direct PCR. Preliminary investigations showed direct STR typing resulted in more alleles compared to conventional STR typing. We then further investigated the following factors with direct STR typing: fabric type (cotton, polyester, and denim), washing method (hand-washing and machine-washing), type of detergents (powder and liquid), washing temperature (cold to 90 °C), pretreatment agents (sodium hypochlorite and hydrogen peroxide), and the number of washes (one, three, and five). Direct PCR could be successfully used for STR typing from laundered bloodstains with very high success rates. Among the three fabric types, only denim negatively affected direct STR typing, while laundering of bloodstains on cotton and polyester had a negligible effect as mostly full profiles were obtained. Multiple washes resulted in a decrease in both the numbers of alleles and peak heights. Surprisingly, washing method, type of detergent, washing temperature, and pretreatment agents only had minimal to no effect on STR profile quality. Due to the robustness and sensitivity of direct STR typing from laundered bloodstains, the method could be beneficial for violent crime investigations in forensic DNA laboratories worldwide.
血迹可能会被清洗或清理以消除犯罪证据。这些操作会降低获得可解释 DNA 谱的机会。先前的研究表明，常规短串联重复（STR）分型会受到与污渍清洗或洗涤相关的各种因素的影响。在这里，我们旨在通过直接 PCR 增加从洗涤血迹中获得可解释 STR 谱的机会。初步研究表明，与常规 STR 分型相比，直接 STR 分型产生了更多的等位基因。然后，我们进一步研究了直接 STR 分型的以下因素：织物类型（棉、聚酯和牛仔布）、洗涤方法（手洗和机洗）、洗涤剂类型（粉末和液体）、洗涤温度（冷至 90°C）、预处理剂（次氯酸钠和过氧化氢）和洗涤次数（一次、三次和五次）。直接 PCR 可成功用于从洗涤血迹中进行 STR 分型，成功率非常高。在三种织物类型中，只有牛仔布对直接 STR 分型产生负面影响，而棉和聚酯上的血迹洗涤几乎没有影响，因为主要获得了完整的谱。多次洗涤会导致等位基因数量和峰高降低。令人惊讶的是，洗涤方法、洗涤剂类型、洗涤温度和预处理剂仅对 STR 谱质量产生最小至无影响。由于直接从洗涤血迹中进行 STR 分型的稳健性和敏感性，该方法可能有助于世界各地法医 DNA 实验室进行暴力犯罪调查。
