Petersen Daniel, Kovacs Frank
Oregon State Police Forensic Services Division, Portland Metro Forensic Laboratory, 13309 SE 84th Avenue, Suite 200, Clackamas, OR 97015.
J Forensic Sci. 2014 Mar;59(2):481-4. doi: 10.1111/1556-4029.12352. Epub 2013 Dec 6.
Presumptive tests for blood play a critical role in the examination of physical evidence and in the determination of subsequent analysis. The catalytic power of hemoglobin allows colorimetric reactions employing phenolphthalein (Kastle-Meyer test) to indicate "whether" blood is present. Consequently, DNA profiles extracted from phenolphthalein-positive stains are presumed to be from blood on the evidentiary item and can lead to the identification of "whose" blood is present. Crushed nodules from a variety of legumes yielded phenolphthalein false-positive reactions that were indistinguishable from true bloodstains both in color quality and in developmental time frame. Clothing and other materials stained by nodules also yielded phenolphthalein false-positive reactivity for several years after nodule exposure. Nodules from leguminous plants contain a protein (leghemoglobin) which is structurally and functionally similar to hemoglobin. Testing of purified leghemoglobin confirmed this protein as a source of phenolphthalein reactivity. A scenario is presented showing how the presence of leghemoglobin from nodule staining can mislead investigators.
血液的预试验在物证检验及后续分析的判定中起着关键作用。血红蛋白的催化能力使得采用酚酞的比色反应（卡斯尔 - 迈耶试验）能够指示是否存在血液。因此，从酚酞阳性污渍中提取的DNA图谱被假定来自物证上的血液，并且能够确定存在的是“谁的”血液。来自多种豆类的压碎结节产生了酚酞假阳性反应，在颜色质量和显色时间框架上都与真正的血迹难以区分。被结节染色的衣物和其他材料在接触结节后的数年里也产生了酚酞假阳性反应。豆科植物的结节含有一种蛋白质（豆血红蛋白），其在结构和功能上与血红蛋白相似。对纯化豆血红蛋白的测试证实了这种蛋白质是酚酞反应性的来源。文中呈现了一个场景，展示了结节染色产生的豆血红蛋白如何误导调查人员。
