Forensic isoscapes based on intra-individual temporal variation of δ¹⁸O and ²⁰⁶Pb/²⁰⁷Pb in human teeth

Abstract

Isotopic signatures used in the georeferencing of human remains are largely fixed by spatially distinct geologic and environmental processes. However, location-dependent temporal changes in these isotope ratios should also be considered when determining an individual's provenance and/or trajectory. Distributions of the relevant isotopes can be impacted by predictable external factors such as climate change, delocalisation of food and water sources and changes in sources and uses of metals. Using Multi-Collector Inductively-Coupled Plasma Mass Spectrometer (MC-ICP-MS) analyses of 206 Pb/ 207 Pb in tooth enamel and dentin from a population of 21 ± 1-year-old individuals born circa 1984 and isotope ratio mass spectrometry (IRMS) of d 18 O in their enamel, we examined the expected influence of some of these factors. The resulting adjustments to the geographic distribution of isotope ratios (isoscapes) found in tooth enamel and dentin may contain additional useful information for forensic identification, but the shifts in values can also impact the uncertainty and usefulness of identifications if they are not taken into account. KEY POINTS Isoscapes of 206 Pb/ 207 Pb and d 18 O used for geolocation are not static. Within a few years, the enamel and dentin of a person may exhibit measurable differences in 206 Pb/ 207 Pb even without changing locations. Changes in climatic patterns tied to rising temperatures are more significant than the direct effect of increasing temperature on d 18 O fixed in tooth bioapatite. Third molar (M3) enamel mineralisation includes material incorporated from before formal amelogenesis takes place.

The use of stable isotopes in postconflict forensic identification

“…Because there are relatively few databases of isotope test results for modern human bone and teeth, isoscapes based on human tissues are unavailable for most world regions. One notable exception is the publication of Pb and O tooth enamel isoscapes for the continental U.S. (Keller et al, 2016; Regan et al, 2021). There are some additional tissue isotope reference data sets available; they are discussed in Section 3.…”

“…Finally, some studies have found lead isotope ratios to be potentially useful for geolocation and thus human identification (Kamenov & Curtis, 2017; Keller et al, 2016; Regan et al, 2021). Similar to Sr, Pb can substitute for calcium in bone and teeth.…”

“…Often stable isotope ratio analysis can be combined with other types of forensic analyses to assist in generating leads and steering identification efforts (i.e., Ambers et al, 2021;Trammell et al, 2018). Finally, some studies have found lead isotope ratios to be potentially useful for geolocation and thus human identification (Kamenov & Curtis, 2017;Keller et al, 2016;Regan et al, 2021). Similar to Sr, Pb can substitute for calcium in bone and teeth.…”

Identification of a female murder victim found in Burgenland, Austria in 1993

“…note that the error bars are smaller than the size of the symbols. The isotopic range of the limited Pb isotope data of German tooth enamel (n = 6) and hair samples (n = 13) from our unpublished data lie on the main data array with 206 Pb/ 207 Pb between 1.147 and 1.172. additional Us Pb isotope data from air Force cadets can be found in regan et al[39].…”