Fingernails as Recorders of Region-of-Origin and Travel History

As Submitted By Proposer: The investigative need to understand and reconstruct an individual's origin or travel is of importance to law enforcement agencies. Investigations of murder, terrorist activities, illegal immigration, and human trafficking all benefit from a quantitative tool that reconstructs region of-origin and travel history. Here I propose to investigate how stable isotope analyses of human fingernails can be used to reconstruct an individual's movements. I hypothesize that human fingernails serve as linear recorders of environmental information through endogenous (food and drinking water) and exogenous (bathing water) inputs. From the literature, I know that carbon and nitrogen isotopes of the keratin protein found in hair and in fingernails reflect dietary inputs, while oxygen isotopes of keratin and strontium isotopes trapped among keratin sheets reflect local tap water (a geographic signal). While a limited number of studies have shown that oxygen and strontium isotope ratios in human hair can provide a geographic signal, such studies have not yet been conducted yet with fingernails. The primary objective of this study is to determine the extent to which 87Sr/86Sr and ä18O isotope ratio values of human fingernails are useful as diagnostic tools of geographic movement, similar to studies that are establishing the forensic utility of stable isotope analysis of scalp hair. To assess this objective I ask two questions: (1) do oxygen and strontium isotope ratios in human fingernails reflect region-of-origin or recent travel and (2) do isotope ratios in fingernails show similar patterns and fidelity to human scalp hair? To examine these questions the proposed research I will analyze fingernail and hair samples from "resident" and "immigrant" volunteers collected over a 1-year period. I hypothesize changes in fingernail oxygen and strontium isotope ratios of immigrants as they acquire a Utah isotopic signature. I hypothesize that hair and fingernail samples will display similar isotopic patterns. The significance of the proposed study is that it may provide law enforcement with a new quantitative trace evidence tool to reconstruct an individual's region-of-origin or recent movements. ca/ncf