Cavalcanti D R, Silva L P
Embrapa Recursos Genéticos e Biotecnologia, Laboratório de Nanobiotecnologia (LNANO), Brasília, 70770-917 DF, Brazil; Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-graduação em nanociência e Nanobiotecnologia, Brasília, 70910-900 DF, Brazil; Polícia Técnico-Científica, Instituto de Criminalística Leonardo Rodrigues, Goiânia, 74425-030 GO, Brazil.
Embrapa Recursos Genéticos e Biotecnologia, Laboratório de Nanobiotecnologia (LNANO), Brasília, 70770-917 DF, Brazil; Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-graduação em nanociência e Nanobiotecnologia, Brasília, 70910-900 DF, Brazil.
Forensic Sci Int. 2019 Aug;301:254-262. doi: 10.1016/j.forsciint.2019.05.048. Epub 2019 May 30.
Bloodstains can provide important information about a criminal act. These biological traces, when analyzed at murder sites, for example, can determine the dynamics of a criminal offense, the identity of a suspect, and the time at which a crime was committed. Determine the time since deposition (TSD) of these blood traces may be the first clue for the police investigators to estimate the time-lapse of a murder. During a criminal attack, the blood spilled from an injury begins the process of degradation and aging from the moment it leaves the human body and comes into contact with the physical environment. The biophysical properties (morphology and elasticity) of red blood cells (RBCs) undergo several changes when outside the human body, which can be analyzed using microscopic techniques such as atomic force microscopy (AFM). Aiming to apply the AFM/force spectroscopy techniques in the analysis of criminal traces, the present study investigated the TSD for blood smears by analyzing possible changes in the RBCs of a group of voluntary donors. Also, we investigated whether there was any difference in TSD analysis after blood smears deposition onto three different surfaces (glass, metal, or ceramic); and finally, we evaluated force×distance curves obtained from deformation of the membrane surface of RBCs as a function of time. The qualitative results apparently showed that there is no perceptible difference in the structure of RBCs when AFM images were analyzed by simple visual comparison over 28 days (T0-T5). Nevertheless, our quantitative results, measured by AFM, demonstrated the increasing trend of the measurements, such as average height (μm), perimeter (μm), area (μm) and volume (μm) of these cells during that period. Additionally, the type of surface of bloodstain deposition should be considered during analyses for the TSD, and the results obtained on glass, metal, or ceramic supports showed significant differences. Therefore, the use of force spectroscopy to obtain force×distance curves for the forensic science approach has been shown to have applicability for the calculation of TSD in the RBCs present in the blood smears. In spite of the promising observations obtained, the use of AFM in crime scenes still requires the expansion and development of more studies for a definitive evaluation of the TSD for blood spots.
血迹可以提供有关犯罪行为的重要信息。例如，在谋杀现场分析这些生物痕迹时，可以确定犯罪行为的动态、嫌疑人的身份以及犯罪发生的时间。确定这些血迹的沉积时间（TSD）可能是警方调查人员估计谋杀案时间间隔的首要线索。在犯罪袭击过程中，受伤流出的血液从离开人体并与物理环境接触的那一刻起就开始了降解和老化过程。红细胞（RBC）的生物物理特性（形态和弹性）在人体外会发生多种变化，可以使用原子力显微镜（AFM）等微观技术进行分析。为了将AFM/力谱技术应用于犯罪痕迹分析，本研究通过分析一组自愿献血者红细胞的可能变化来研究血涂片的TSD。此外，我们研究了血涂片沉积在三种不同表面（玻璃、金属或陶瓷）后TSD分析是否存在差异；最后，我们评估了从红细胞膜表面变形获得的力×距离曲线随时间的变化。定性结果显然表明，在28天（T0 - T5）内通过简单视觉比较分析AFM图像时，红细胞结构没有明显差异。然而，我们通过AFM测量的定量结果表明，在此期间这些细胞的测量值呈上升趋势，如平均高度（μm）、周长（μm）、面积（μm）和体积（μm）。此外，在分析TSD时应考虑血迹沉积表面的类型，在玻璃、金属或陶瓷载体上获得的结果显示出显著差异。因此，已证明使用力谱法获得力×距离曲线的法医科学方法适用于计算血涂片中红细胞的TSD。尽管获得了有前景的观察结果，但在犯罪现场使用AFM仍需要开展更多研究以进行扩展和发展，以便对血斑的TSD进行最终评估。
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