Strasser Stefan, Zink Albert, Kada Gerald, Hinterdorfer Peter, Peschel Oliver, Heckl Wolfgang M, Nerlich Andreas G, Thalhammer Stefan
Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Munich, Germany.
Forensic Sci Int. 2007 Jul 20;170(1):8-14. doi: 10.1016/j.forsciint.2006.08.023. Epub 2006 Nov 13.
We present a new tool for the estimation of the age of bloodstains, which could probably be used during forensic casework. For this, we used atomic force microscopy (AFM) for high-resolution imaging of erythrocytes in a blood sample and the detection of elasticity changes on a nanometer scale. For the analytic procedure we applied a fresh blood spot on a glass slide and started the AFM detection after drying of the blood drop. In a first step, an overview image was generated showing the presence of several red blood cells, which could easily be detected due to their typical "doughnut-like" appearance. The consecutively morphological investigations in a timeframe of 4 weeks could not show any alterations. Secondly, AFM was used to test the elasticity by recording force-distance curves. The measurements were performed immediately after drying, 1.5 h, 30 h and 31 days. The conditions were kept constant at room temperature (20 degrees C) and a humidity of 30%. The obtained elasticity parameters were plotted against a timeline and repeated several times. The elasticity pattern showed a decrease over time, which are most probably influenced by the alteration of the blood spot during the drying and coagulation process. The preliminary data demonstrates the capacity of this method to use it for development of calibration curves, which can be used for estimation of bloodstain ages during forensic investigations.
我们提出了一种用于估计血迹年龄的新工具，该工具可能会在法医案件工作中使用。为此，我们使用原子力显微镜（AFM）对血样中的红细胞进行高分辨率成像，并检测纳米尺度上的弹性变化。对于分析过程，我们在载玻片上滴加新鲜血斑，血滴干燥后开始进行AFM检测。第一步，生成一幅概述图像，显示出几个红细胞的存在，由于其典型的“甜甜圈状”外观，很容易被检测到。在4周的时间内进行的连续形态学研究未显示出任何变化。其次，使用AFM通过记录力-距离曲线来测试弹性。测量在干燥后立即进行，以及在1.5小时、30小时和31天时进行。条件保持恒定，室温为20摄氏度，湿度为30%。将获得的弹性参数与时间线作图，并重复多次。弹性模式显示随时间下降，这很可能受到血斑在干燥和凝血过程中的变化影响。初步数据证明了该方法用于建立校准曲线的能力，该校准曲线可用于法医调查中估计血迹的年龄。
