School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia.
Analyst. 2018 Aug 20;143(17):4027-4039. doi: 10.1039/c7an01615h.
Latent fingermarks are an important form of crime-scene trace evidence and their usefulness may be increased by a greater understanding of the effect of chemical distribution within fingermarks on the sensitivity and robustness of fingermark detection methods. Specifically, the relative abundance and micro-distribution of sebaceous (lipophilic) and eccrine (hydrophilic) material in fingermarks have long been debated in the field, yet direct visualisation of relative abundance and micro-distribution was rarely achieved. Such a visualisation is nonetheless essential to provide explanations for the variation in reproducibility or robustness of latent fingermark detection with existing methods, and to identify new strategies to increase detection capabilities. In this investigation, we have used SR-ATR-FTIR and confocal Raman microscopy to probe the spatial micro-distribution of the sebaceous and eccrine chemical components within latent fingermarks, deposited on non-porous surfaces. It was determined that fingermarks exhibit a complex spatial distribution, influenced by the ratio of lipophilic to aqueous components, and to a first approximation resemble a water-in-oil or oil-in-water emulsion. Detection of a substantial lipid component in "eccrine enriched fingermarks" (wherein hands are washed to remove lipids) is noteworthy, as it provides a potential explanation for several scenarios of unexpected fingermark detection using methods previously thought unsuitable for "eccrine deposits". Furthermore, the pronounced distribution of lipids observed in natural fingermark deposits was intriguing and agrees with recent discussion in this research field that natural fingermarks contain a much higher lipid content than previously thought.
潜伏指纹是犯罪现场痕迹证据的重要形式，通过更深入地了解指纹内化学物质分布对指纹检测方法的灵敏度和稳健性的影响，可以提高其可用性。具体来说，指纹中皮脂（亲脂性）和汗腺（亲水性）物质的相对丰度和微观分布长期以来一直是该领域争论的焦点，但很少直接观察到相对丰度和微观分布。然而，这种可视化对于解释现有方法中潜伏指纹检测的重现性或稳健性的变化以及确定新的策略来提高检测能力至关重要。在这项研究中，我们使用衰减全反射傅里叶变换红外光谱（SR-ATR-FTIR）和共聚焦拉曼显微镜来探测潜伏指纹中皮脂和汗腺化学物质在非多孔表面上的空间微观分布。结果表明，指纹表现出复杂的空间分布，受亲脂性与水性成分的比例影响，并且在第一近似中类似于水包油或油包水乳液。值得注意的是，在“富含汗腺的指纹”（其中用水清洗以去除脂质）中检测到大量脂质成分，因为它为几种使用先前认为不适合“汗腺沉积物”的方法进行意外指纹检测的情况提供了潜在解释。此外，在天然指纹沉积物中观察到的明显脂质分布令人着迷，并且与该研究领域最近的讨论一致，即天然指纹中所含的脂质含量比以前认为的要高得多。
