Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON, Canada.
Geology & Geochemistry Cluster, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
PLoS One. 2022 Oct 26;17(10):e0275902. doi: 10.1371/journal.pone.0275902. eCollection 2022.
Unidentified human remains have historically been investigated nationally by law enforcement authorities. However, this approach is outdated in a globalized world with rapid transportation means, where humans easily move long distances across borders. Cross-border cooperation in solving cold-cases is rare due to political, administrative or technical challenges. It is fundamental to develop new tools to provide rapid and cost-effective leads for international cooperation. In this work, we demonstrate that isotopic measurements are effective screening tools to help identify cold-cases with potential international ramifications. We first complete existing databases of hydrogen and sulfur isotopes in human hair from residents across North America by compiling or analyzing hair from Canada, the United States (US) and Mexico. Using these databases, we develop maps predicting isotope variations in human hair across North America. We demonstrate that both δ2H and δ34S values of human hair are highly predictable and display strong spatial patterns. Multi-isotope analysis combined with dual δ2H and δ34S geographic probability maps provide evidence for international travel in two case studies. In the first, we demonstrate that multi-isotope analysis in bulk hair of deceased border crossers found in the US, close to the Mexico-US border, help trace their last place of residence or travel back to specific regions of Mexico. These findings were validated by the subsequent identification of these individuals through the Pima County Office of the Medical Examiner in Tucson, Arizona. In the second case study, we demonstrate that sequential multi-isotope analysis along the hair strands of an unidentified individual found in Canada provides detailed insights into the international mobility of this individual during the last year of life. In both cases, isotope data provide strong leads towards international travel.
历史上，执法机关一直在全国范围内调查身份不明的人类遗骸。然而，在全球化的世界中，这种方法已经过时了，因为人们可以通过快速的交通工具轻易地跨越国界长途旅行。由于政治、行政或技术方面的挑战，跨境合作解决冷案的情况很少见。开发新工具以提供快速和具有成本效益的国际合作线索至关重要。在这项工作中，我们证明了同位素测量是有效的筛选工具，可以帮助识别可能具有国际影响的冷案。我们首先通过编译或分析来自加拿大、美国和墨西哥的头发，完成了北美居民头发中氢和硫同位素的现有数据库。利用这些数据库，我们开发了预测北美人发同位素变化的地图。我们证明，头发的 δ2H 和 δ34S 值都具有高度可预测性，并显示出强烈的空间模式。多同位素分析结合双 δ2H 和 δ34S 地理概率图为两个案例研究中的国际旅行提供了证据。在第一个案例中，我们证明了对在靠近美墨边境的美国发现的死亡越境者的头发进行的多同位素分析有助于追踪他们的最后居住地或返回墨西哥的特定地区。这些发现随后通过亚利桑那州图森市皮马县法医办公室对这些人的身份识别得到了验证。在第二个案例研究中，我们证明了对在加拿大发现的一名身份不明者的头发进行的顺序多同位素分析提供了有关该人在生命的最后一年国际流动性的详细信息。在这两种情况下，同位素数据都提供了有关国际旅行的重要线索。
