Di Junyi, Jin Jing, Zhang Jinzhuan, Xu Xiaoning, Li Chen, Guo Keli, Shi Chaoyi
School of Graduate, China People's Police University, Langfang 065000, China.
School of Criminal Investigation, China People's Police University, Langfang 065000, China.
Forensic Sci Int Genet. 2025 Jan;74:103172. doi: 10.1016/j.fsigen.2024.103172. Epub 2024 Nov 5.
The identification of biological evidence is particularly important for criminal detection, and the deoxyribonucleic acid (DNA) analysis plays a significant role in reconstructing events. However, bloodstains after thermal exposure in fires are quite unique compared to those in other scenes. Previous results regarding DNA recovery in bloodstains after heating are inconsistent with each other, which limits guidance for forensic science. In order to confirm the influence of heat on DNA recovery, the important physical evidence, bloodstain, was selected for its common occurrence, and a standard heat source, the Cone Calorimeter, was used to simulate high temperatures in fire scenes. A series of bloodstains were prepared under different heating conditions, and the results of short tandem repeat (STR) typing were systematically correlated with the trace characteristics of bloodstains. The findings indicate that heating bloodstains below 150 °C for less than 10 mins has minimal effect on DNA testing. After heating bloodstains at 150 °C for 20 mins or at 180 °C for 5 mins, partial DNA profiles were obtained, accompanied by blackening and cracking of the bloodstains. After exposure to 180 °C for 20 mins or 200 °C for 10 mins, no DNA profiles were obtained with bloodstains exhibiting metallic lusters and black bulges. Furthermore, from the perspective of chemical bond energy, the C-N, C-O, C-C, and P-O bonds in DNA molecules are prone to breaking during heating. The C-N bond serves as the primary connection between the four bases and the strand, while the C-O, C-C, and P-O bonds are significant connections within the DNA strand. It is thus hypothesized that the breakage of any bond aforementioned during heating results in the failure of DNA typing. Understanding the correlation between trace characteristics of bloodstains and DNA typing results after thermal exposure is crucial for comprehending DNA recovery from physical evidence collected from fire scenes.
生物证据的识别对刑事侦查尤为重要，而脱氧核糖核酸（DNA）分析在事件重建中发挥着重要作用。然而，与其他场景中的血迹相比，火灾中热暴露后的血迹相当独特。以往关于加热后血迹中DNA回收的结果相互矛盾，这限制了对法医学的指导作用。为了确认热对DNA回收的影响，选择了常见的重要物证血迹，并使用标准热源锥形量热仪模拟火灾现场的高温。在不同加热条件下制备了一系列血迹，并将短串联重复序列（STR）分型结果与血迹的微量特征进行了系统关联。研究结果表明，在150℃以下加热血迹10分钟以内对DNA检测影响最小。在150℃加热20分钟或180℃加热5分钟后，获得了部分DNA图谱，同时血迹出现变黑和开裂。在180℃暴露20分钟或200℃暴露10分钟后，未获得DNA图谱，血迹呈现金属光泽和黑色凸起。此外，从化学键能的角度来看，DNA分子中的C-N、C-O、C-C和P-O键在加热过程中容易断裂。C-N键是四个碱基与链之间的主要连接，而C-O、C-C和P-O键是DNA链内的重要连接。因此推测，加热过程中上述任何一种键的断裂都会导致DNA分型失败。了解热暴露后血迹的微量特征与DNA分型结果之间的相关性，对于理解从火灾现场收集的物证中DNA的回收情况至关重要。
