Development of Original Stable Isotope Forensic Reference Standards for Human Geographic Origin Attribution in Nigeria

Stable isotope analysis of human biological tissues offers forensic investigators a scientifically rigorous method for estimating an individual's geographic origin, a capability of critical importance in unidentified remains cases, trafficking investigations, and disaster victim identification. This doctoral study makes an original contribution to Nigerian forensic science by developing stable isotope reference standards for human geographic origin attribution across the country's geopolitical zones. A systematic biogeographic sampling design was employed, collecting 480 hair, nail, and enamel samples from 120 documented volunteers resident for over five years in targeted locations across South East, South West, South South, North Central, North West, and North East Nigeria. Samples were analysed by isotope ratio mass spectrometry for oxygen, hydrogen, carbon, nitrogen, and strontium isotope ratios. Multivariate isoscapes were constructed integrating sample isotope data with environmental isotope predictors including precipitation isoscape models, soil geochemistry, and dietary pattern data. The resulting Nigeria Forensic Isotope Atlas achieves correct geopolitical zone attribution in eighty-seven percent of test cases, with highest resolution in ecologically distinct zones such as the Sahel and Niger Delta. Original isoscape models developed in the study represent the first published forensic stable isotope reference system specific to Nigerian populations. Recommendations include embedding the Nigeria Forensic Isotope Atlas within national forensic investigation protocols for unidentified remains and trafficking victim cases. Keywords: stable isotope analysis, geographic origin, forensic anthropology, Nigeria, isoscape.