A Comprehensive Test of the Methods and Models Used to Assign Geographic Origin to Human Skeletal Remains With Stable Isotope Data

As submitted by the proposer: This project will provide a comprehensive test of the analysis methods and prediction models used to assign origin to human skeletal remains using stable isotopes. Application of stable isotope measurements to unidentified remains can complement traditional biometrics—fingerprint examination, odontology, and DNA analysis—by revealing information about an individual’s life history. Yet many of the isotopic methods and models available for use in modern forensic investigations originate from classic research done in archaeological settings using a mixture of bone and teeth. Foundational oxygen isotope models were built from measurements made on the phosphate component of bone and teeth while current analytical procedures typically measure the carbonate component, requiring data transformation before origin assignment. Strontium isotope models generally assume direct correlations between the isotope signatures of environment and tissue, although few studies have tested this assumption. Here, our goal is to challenge current analysis methods and origin assignment models using oxygen and strontium isotope ratios of paired bone and teeth from 50 modern decedents of known origin, collected from remains donated for research. Measured isotope ratios should reflect the isotope signatures of the individual’s inputs during life. We will collect information on each decedent’s known area of residence in the years prior to death, when the bone was last remodeled, and during early adulthood, when tooth enamel formed. We will answer a series of questions during this project: What is the relationship between oxygen isotope signatures of carbonate in bioapatite and an individual’s location? What is the relationship between strontium isotope signatures of whole bone or tooth enamel and an individual’s location? Are separate prediction models needed for bones and teeth? These answers will allow us to determine which methods and models are fit-for-purpose for use in modern criminal justice settings to assign origin to human skeletal remains using stable isotopes. IsoForensics, Inc. will provide stable isotope analyses and subsequent data interpretation during this proposed research. Key personnel have nationally recognized reputations in their fields and have been involved with projects of interest to the U.S. Department of Justice. Ultimately, we hope that updates to the stable isotope analysis methods and origin assignment models used in investigations of skeletal remains will aid in individual identification, bringing closure to some of the 10,000+ unidentified decedent cases currently listed with the National Missing and Unidentified Persons System (NamUS) and housed in medical examiner offices across the U.S. Note: This project contains a research and/or development component, as defined in applicable law. ca/ncf