Institute of Forensic Science, Fudan University, Shanghai, 200032, PR China.
Shanghai Key Laboratory of Forensic Medicine, Shanghai Forensic Service Platform, Ministry of Justice, Academy of Forensic Science, Shanghai, 200063, PR China.
Int J Legal Med. 2024 Nov;138(6):2325-2330. doi: 10.1007/s00414-024-03302-3. Epub 2024 Aug 7.
DNA mixture analysis poses a significant challenge in forensic genetics, particularly when dealing with degraded and trace amount DNA samples. Multi-SNPs (MNPs) are genetic markers similar to microhaplotypes but with smaller molecular sizes (< 75 bp), making them theoretically more suitable for analyzing degraded and trace amount samples. In this case report, we investigated a cold case involving a campstool stored for over a decade, aiming to detect and locate the suspect's DNA. We employed both conventional capillary electrophoresis-based short tandem repeat (CE-STR) analysis and next-generation sequencing-based multi-SNP (NGS-MNP) analysis. The typing results and deconvolution of the mixed CE-STR profiles were inconclusive regarding the presence of the suspect's DNA in the mixed samples. However, through NGS-MNP analysis and presence probability calculations, we determined that the suspect's DNA was present in the samples from Sect. 4-1 with a probability of 1-8.41 × 10 (99.999159%). This evidence contradicted the suspect's statement and aided in resolving the case. Our findings demonstrate the significant potential of MNP analysis for examining degraded and trace amount DNA mixtures in forensic investigations.
DNA 混合分析在法医学遗传学中是一个重大挑战，特别是在处理降解和微量 DNA 样本时。多单核苷酸多态性（MNPs）是类似于微单倍型的遗传标记，但分子大小更小（<75bp），理论上更适合分析降解和微量样本。在本案例报告中，我们调查了一个冷藏案件，涉及一个存放了十多年的露营凳，旨在检测和定位嫌疑人的 DNA。我们同时采用了传统的基于毛细管电泳的短串联重复序列（CE-STR）分析和基于下一代测序的多单核苷酸多态性（NGS-MNP）分析。混合 CE-STR 图谱的分型结果和去卷积对于混合样本中嫌疑人 DNA 的存在没有明确结论。然而，通过 NGS-MNP 分析和存在概率计算，我们确定嫌疑人的 DNA 存在于第 4-1 节的样本中，概率为 1-8.41×10（99.999159%）。这一证据与嫌疑人的陈述相矛盾，有助于解决案件。我们的发现表明 MNP 分析在法医学调查中检查降解和微量 DNA 混合物的巨大潜力。
