College of Science and Engineering, Flinders University, Bedford Park, South Australia, Australia.
Forensic Science SA, GPO Box 2790, Adelaide 5001, Australia.
Forensic Sci Int Genet. 2024 Nov;73:103101. doi: 10.1016/j.fsigen.2024.103101. Epub 2024 Aug 2.
The sensitivity of DNA analysis has progressed to the point that trace levels of DNA, originating from only a few cells, can generate informative profiles. This means that virtually any item or surface can be sampled with a reasonable chance of obtaining a DNA profile. As the presence of DNA does not suggest how it was deposited, questions are often raised as to how the DNA came to be at a particular location and the activity that led to its deposition. Therefore, understanding different modes of DNA deposition, reflective of realistic forensic casework situations, is critical for proper evaluation of DNA results in court. This study aimed to follow the movements of DNA to and from individuals and common household surfaces in a residential premises, while socially interacting. This took place over an hour and involved four participants, with known shedder status, designated as visitors (a male and a female) and hosts (a male and a female), who engaged in the activity of playing a board game while being served food. During the study, the participants were instructed to use the toilet on a single occasion to assess the transfer of DNA to new and unused underwear that was provided. All contacts made by the participants in the dining room and kitchen were video recorded to follow the movements of DNA. Samples were collected based on the history of contact, which included hands, fingernails and penile swabs. Direct contacts resulted in detectable transfer (LR > 1) in 87 % (87/100) of the non-intimate samples and clothing. For surfaces touched by multiple participants, DNA from the person who made the last contact was not always detectable. The duration and number of contacts did not significantly affect the detection of the person contacting the item. On the other hand, presence of background DNA and participant's shedder status appear to play an important role. Further, unknown contributors were detected in the majority of samples. Finally, indirect transfer was observed on a number of occasions including co-habiting partners of guests who were not present at the study location. The results of this study may assist with decision making for exhibit selection or targeting areas for sampling within the home environment. Our findings can also be used in conjunction with previous literature to develop activity-level evaluations in such situations where the source of the DNA is conceded, but the mode of deposition is disputed.
DNA 分析的灵敏度已经发展到可以从仅几个细胞产生的痕量 DNA 中生成有信息的图谱的程度。这意味着几乎任何物品或表面都可以进行采样，并且有很大的机会获得 DNA 图谱。由于 DNA 的存在并不能说明它是如何沉积的，因此经常会出现关于 DNA 如何出现在特定位置以及导致其沉积的活动的问题。因此，了解 DNA 沉积的不同模式，反映现实法医工作情况，对于正确评估法庭上的 DNA 结果至关重要。本研究旨在跟踪 DNA 在住宅内个人和常见家庭表面之间的运动，同时进行社交互动。这发生在一个小时内，涉及四个参与者，已知脱落者身份，指定为访客（一男一女）和主人（一男一女），他们在提供食物的同时玩棋盘游戏。在研究过程中，参与者被指示仅使用一次厕所，以评估提供的新的未使用的内衣上的 DNA 转移。参与者在餐厅和厨房的所有接触都被视频记录下来，以跟踪 DNA 的运动。根据接触史收集样本，包括手、指甲和阴茎拭子。直接接触导致 87%（87/100）的非亲密样本和衣物中可检测到的转移（LR > 1）。对于被多个参与者触摸的表面，最后接触该物品的人的 DNA 并不总是可检测到的。接触的持续时间和次数不会显著影响接触物品的人的检测。另一方面，背景 DNA 的存在和参与者的脱落者身份似乎起着重要作用。此外，在大多数样本中检测到未知的贡献者。最后，在许多情况下观察到间接转移，包括不在研究地点的客人的同居伴侣。本研究的结果可能有助于决策制定展品选择或针对家庭环境中的采样区域。我们的发现还可以与以前的文献结合使用，在承认 DNA 来源但对沉积模式有争议的情况下，对此类情况进行活动水平评估。
