Over the years, numerous intriguing applications and cases have confirmed that isotope fingerprints provide conclusive answers for the determination of origin of substances such as drugs, explosives, paints, plastics, or tapes, which can be found at crime scenes. The unlocking of their “hidden” origin casts light on how valuable such an invisible, yet detectable information is, for successfully closing forensic investigations. The post “How Isotope Hunters Are Using Isotope Fingerprints to Solve Criminal Forensic Cases” introduces how isotope fingerprints deliver valuable forensic information and how they are widely used in courts, in conjunction with other techniques, as quantitative empirical evidence that is reproducible and easy to validate.
In the Isotope Fingerprints Compendium for Forensic Investigations some examples of analysis of forensic samples are collected, featuring an introduction to isotope fingerprints and their uses for forensic investigations (download the compendium here).
Some of the examples of the compendium will be presented at the upcoming 7th Conference of the Forensic Isotope Ratio Mass Spectrometry Network (16-19 September, San Michele all’Adige, Italy) where scientists, technicians, and experts interested in forensic application of stable isotope analysis have the opportunity to discuss a variety of topics as well as more general aspects of forensic isotope analysis (read more on the FIRMS conference website).
While the scientific community recognizes isotope fingerprints are a valuable tool for solving the ”classical” forensic cases, in recent papers we see how new cross-disciplinary areas of applications for isotope analysis are being developed, unlocking more information for forensic purposes. In this post we will focus on two: forensic anthropology and forensic isotope ecology.
Applications of Isotope Analysis for Forensic Anthropology
In the recently published paper, Bartelink and Chesson (2019)1 highlighted that “…applications of the (stable isotope) technique to unidentified human remains for forensic profiling purposes are continuing to emerge…”, and presented an overview of medicolegal cases utilizing stable isotope analysis. Traditionally, forensic anthropologists have exploited in-depth scientific evaluations, for example comparative analysis of fingerprints, DNA profiles, dentition, and radiographs, especially for the identification of unknown decedents. However, for the so called “cold-cases” isotope analysis has shown promising results.
By investigating different tissue types, distinct time-scale of a person’s life can be addressed, e.g. bones carry information on diet and location for the past 10-20 years, whereas hair and nails can help reconstruct where a human has recently been. Isotope fingerprints of hair and nail keratin and bone collagen are analyzed to unlock information about a decedent’s residence patterns and dietary choices, to the extent that travel and dietary history for an unidentified decedent can be reconstructed. Measurements of nitrogen and carbon isotope fingerprints in bone collagen have been interpreted reliably as an indicator of human and animal diets because they primarily reflect the protein fraction of the consumer’s diet. As Bartelink and Chesson (2019) report, carbon and nitrogen isotope fingerprints were instrumental to provide conclusive answers for the discovery of a long bone shaft fragment at a construction site in downtown San Francisco in 2016. Conclusion whether the bone was by Native American in origin or not was to have a significant impact on further construction works at the site.
After the macroscopic analysis and histological examination, isotope analysis was used to determine if the bone collagen had carbon and nitrogen isotopic compositions similar to prehistoric Native Americans from the San Francisco Bay Area.
By comparing the isotopic composition of known-origin samples and by unlocking information on the dietary habits, isotope analysis provided strong circumstantial evidence. In this case, the coroner’s office and construction firm accepted the results as support for the bone belonging to a prehistoric Native American.
Applications of Isotope Analysis for Forensic Isotope Ecology
In his latest article on forensic isotope ecology, Wolfram Meier-Augenstein (2019)2 summons examples about real cases and applications emerging in this field. Illegal traffic of endangered species of animals or plants and economically-driven mislabeling of provenance of plants required that ecology studies would adopt an approach that was traditionally used for forensics investigations.
With the use of isotope fingerprints (in some cases in combination with other techniques) important ecological questions about terrestrial and marine food webs, or diet change, and migration patterns of wild birds can now be answered. These questions are the starting points for investigations that help protect wildlife and consumers.
Despite a ban on the international trade in ivory, large numbers of poaching of elephants’ ivory tusks are still recorded. The ivory is often carved into ornaments and jewelry. The ban on international trade was introduced in 1989 by CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) allowing some elephant populations to recover, especially where adequate protection was put in place. Increasing market demand triggered an upsurge in poaching and illegal ivory trafficking in recent years.
Meier-Augenstein (2019) points to a study published in 2016 (Ziegler et al.3) which reported data on carbon, nitrogen, sulfur, oxygen and hydrogen isotope fingerprints of 507 ivory samples. The isotope signatures recorded in elephants’ hair provide insights on their feeding habits and locations. Thanks to this information the researchers were able to infer the accuracy of the assignments of samples from the African elephant species to their correct provenance. The results show that isotopic profiling of African elephant ivory works on regional scales.
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Another named study with a multi-analytical approach is by Natusch et al. (2017)4, reporting how isotopic and elemental markers were used to identify the source and origin of traded python skins. Phyton skins trade is protected and regulated by an international agreement, which aims at preventing illegal importation and mislabeling of products that could be used to incentive illegal business. By combining isotopic and elemental information, authors were able to discriminate between diet treatments and geographic origin of pythons, offering a strong tool for verifying their provenance.
When it comes to plants, the determination of their geographic origin is also of interest where origin is associated with economically-driven value creation for consumers. For example, a wrongful declaration of origin of cotton may lead to fraudulent labeling to increase sales of products or to avoid/reduce import duty, damaging the market for original products and affecting consumers.
These examples show how isotope hunters are continuing to expand the uses of isotope fingerprints: from a traditional approach to forensic aimed at identifying origin and authenticity to give more clues for forensic investigations moving to applications which require a multidisciplinary approach.
Do you work with other examples for forensics applications? Share them in the comment section below!
To learn more about how isotope fingerprints are used for forensics cases click on the resources below:
- Read more: Why use isotope for forensics investigations
- Read more: Examples of IRMS being used in forensic settings
- Attend the webinar: Determining Provenance of Insects with Isotope Analysis for Biosecurity Purposes: Real World Forensic Applications
- Read More: download the Isotope Fingerprints compendium for forensics investigations
Follow the adventure of the Isotope Hunter as he investigates the origin and authenticity of samples with isotope fingerprints. Using isotope ratio mass spectrometry (IRMS), the Isotope Hunter gains access to information on geographic region, botanical processes, soil and fertilization processes, and fraudulent practices. Are you an Isotope Hunter? Investigate here.
1E. J. Bartelink & L. A. Chesson (2019) Recent applications of isotope analysis to forensic anthropology, Forensic Sciences Research, 4:1, 29-44.
2W. Meier-Augenstein (2019) From stable isotope ecology to forensic isotope ecology — Isotopes’ tales, Forensic Science International, 300, 89–98.
3S. Ziegler, S. Merker, B. Streit, M. Boner, D. E. Jacob (2016) Towards understanding isotope variability in elephant ivory to establish isotopic profiling and source area determination, Biological Conservation, 197, 154–163.
4D. J. D. Natusch, J. F. Carter, P. W. Aust, N. V. Tri, U. Tinggi, Mumpuni, A. Riyanto, J. A. Lyons, Serpent’s source: determining the source and geographic origin of traded python skins using isotopic and elemental markers, Biological Conservation, 209, 406–414.