Application of Stable Isotope Variation in Human Tissues to Problems in Identification

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Abstract
Variation in the stable isotope composition of human tissues and fluids suggests the use of such data as an aid in identification of unknown human remains. Carbon isotope values vary depending specifically on the photosynthetic pathways utilized by plants consumed as feed by domesticated animals, and by humans directly. Sulphur isotopes vary depending on environmental sulphur in the atmosphere and lithosphere, and stable isotopes of oxygen, nitrogen and hydrogen also vary in predictable manners in different geographic locations. The use of a multi-element approach is demonstrated as a means of narrowing down the possible place of residence of unidentified human remains. Carbon and sulphur isotope ratios were determined on samples of human hair from five countries. Results show that while values for one element may be similar for samples from diverse regions, values for a second element differ such that samples are distinguishable. Hair samples from three regions of Canada were analysed for carbon isotopes. Differences are due to latitude and diet. Analysis of tissues and fluids with varying turnover rates may be useful in distinguishing long term residence from short term travel. Experiments on one individual show that δ18O and δ34S values changed on an extended stay in Japan then returned to normal values shortly after return to Canada.