Although isotope ratio mass spectrometry (IRMS) has historically been considered a specialized technique, requiring significant training and expertise, modern instruments provide such automation and ease-of-use that it is becoming easier to conduct  and a more common tool for answering a variety of forensic, ecological, geological, anthropological and environmental questions. In the forensic community, IRMS is already in use in many government forensic laboratories and has been used as an investigative lead on several occasions. This presentation provides three different studies involving source attribution using IRMS, all of which make use of multivariate isotope ratios from compound-specific IRMS to offer greater discrimination than bulk isotope analysis.<br/>In the first part of the talk, we compare the ability of bulk and compound-specific isotope analysis to classify and attribute human hair to subject groups such as body mass index, age and sex. The compound-specific isotope ratio analysis was performed on 14 underivatized amino acids that were released from the hair following acid hydrolysis.  Statistical techniques such as canonical discriminant analysis (CDA) are used to overlook the covariance of amino acid isotope ratios between individuals caused by dietary factors and instead highlight the selective differences caused by grouping factor(s) such as age and sex. Samples originate form both US and Jordanian subjects.<br/>The second part of the talk uses isotope ratios to link blowfly larvae, pupae and adult flies to different food (carrion) sources. Ecologists often use isotope ratio analysis to determine the trophic level of organisms and their primary food sources. However, such analyses are rarely interested in linking adult insects to a specific meat source in a forensic context. In this study, we present a proof of concept study to test the hypothesis that adult blowflies can be linked to specific food sources via their stable isotope ratios.<br/>The final part applies the same method (amino-acid-specific IRMS) to predict the geographic harvesting area of eastern Oysters. Such capabilities are a potential way to prevent against consumer fraud, public health and illegal harvesting. The three selected applications are just three examples of using compound-specific isotope analysis (CSIA) to unlock the origins of matter for potential societal benefit.

Forensic attribution using stable isotopes: Hairs to humans and insects to carrion

253rd National Meeting (2017)

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