Abstract：
Being able to attest when a bloodstain was deposited at a crime scene can be invaluable to a prosecution process, and methods to provide that information have long been desired. Determining the Time since Deposition (TsD) of a trace would allow placing a subject both in space and time to the crime scene-or prove that a trace left by that person was unrelated to it because it was deposited before or after the time the crime had occurred. To this day, no method for TsD determination has made its way into routine forensic casework, mainly because of the numerous challenges that await when trying to understand and account for all the influencing and confounding factors that affect the aging process (such as, e.g., temperature, UV-light exposure, or humidity). Here, we present an untargeted metabolomics-based study using liquid chromatography high-resolution mass spectrometry (LC-HR-MS) and data-dependent acquisition to analyze blood samples aged under two distinctly different storage conditions over 48 weeks. Global differences in age- and storage-dependent changes in blood metabolomes were described, and TsD-classification strategies based on qualitative and quantitative assessment of molecular features (MFs) have been proposed. Based on the selected criteria to best predict the TsD, the dipeptide Phenylalanylalanine (PheAla) can be considered as a promising candidate for TsD prediction. In essence, changes in the blood metabolome dynamics showed a strong association with increasing TsD, but significant differences depending on storage conditioning were observed, facilitating the need to study further the influence of individual influencing factors on TsD determination.
摘要：
能够证明血迹何时沉积在犯罪现场对起诉过程来说是非常宝贵的，以及提供该信息的方法长期以来一直是人们所期望的。确定痕迹的自沉积时间（TsD）将允许将对象在空间和时间上都放置到犯罪现场-或证明该人留下的痕迹与之无关，因为它是在犯罪发生之前或之后存放的。直到今天,没有确定TsD的方法进入常规的法医案件工作，主要是因为在试图理解和解释影响衰老过程的所有影响和混杂因素时面临的众多挑战(例如，例如，温度,紫外线曝光，或湿度)。这里,我们提出了一项基于非靶向代谢组学的研究,该研究使用液相色谱高分辨率质谱(LC-HRMS)和数据依赖性采集来分析在两种截然不同的储存条件下老化超过48周的血液样本.描述了血液代谢组年龄和储存依赖性变化的全球差异，并提出了基于分子特征（MFs）的定性和定量评估的TsD分类策略。基于选择的标准来最好地预测TsD，二肽苯丙丙氨酸（PheAla）可以被认为是TsD预测的有希望的候选者。实质上,血液代谢组动力学的变化与TsD的增加有很强的相关性，但根据储存条件观察到显著差异，促进需要进一步研究(个体)影响因素对TsD测定的影响。
