Interview with President of IsoForensics Inc., Lesley Chesson

southern-utahDifferent forms of elements–called isotopes–are found everywhere in the environment. These isotopes are incorporated into materials in varying ratios and the abundances of different isotopes thus serve as a record of the material’s formation. Analysis of a material for its distinct isotope signature can subsequently be used to reveal its history. Investigators have applied stable isotope analysis to a variety of materials of forensic interest including drugs, explosives, money, food, ivory, and human remains. For example, the isotopes in human hair protein can reveal the age of an individual, what s/he ate, and even how often (and where) s/he travelled.

What is your professional background and how did you come to be involved in IsoForensics?

I have a master’s degree in biology, with a lot of microbiology and chemistry experience. I entered the world of isotope forensics when I was hired to raise Bacillus subtilis (a cousin of the anthrax bacterium) under a variety of conditions – in liquid media, on agar plates, with different nutrients, etc. Because organisms record information about the environment in the isotopes of their tissues, the goal of this project was to develop models that allowed investigators to predict the growth conditions of a dangerous bacterium–such as anthrax–from its isotopic characteristics.

From its start in academia, IsoForensics developed into a private analytical services and research firm that explored novel forensic applications of isotope analysis. I enjoyed the challenges offered by that exploration. Since my first work on the B. subtilis project, I’ve been involved in other projects on human remains, foods and beverages, illicit drugs, and explosives.

Tell us about the work IsoForensics is involved in and what kind of clients do you typically work with?

Currently, IsoForensics provides a lot of human remains testing in unidentified decedent cases. The goal is to use the isotope records contained in hair, nails, bone, and teeth to reconstruct the travel history of individuals and provide new evidence on their origins: Were they local to the area of discovery? Had they traveled prior to death? Where might they have traveled? We work with a variety of law enforcement groups in this casework.

In addition to service work, we conduct basic and applied research through funded grants and contracts. One recent project has started to investigate the origins and ages of seized elephant ivory to understand the structure of illegal trade networks in Africa and Asia.

What are some of the most common sample types you are asked to analyse, and does anything pose a particular challenge?

In any given month, we can analyze a variety of materials – human and wildlife remains, illicit drugs, explosives, etc. One of the most challenging measurements we make is for strontium isotope ratios. There is so little strontium contained in organic materials that prep work takes place in clean lab settings. The preparation of materials for radiocarbon dating is also challenging since we must be extremely careful about contamination of “old” materials with “modern” carbon. However, these challenges are worthwhile since strontium isotopes can provide potentially useful geolocation data about materials while radiocarbon dating provides quantitative information on the “age” of materials.

Are there any areas of isotopic analysis that could benefit from further research and development?

Yes. Isotope forensics benefits from better and better models/methods for interpreting data. It’s one thing to compare isotope measurement results from sample to sample or from sample to a reference databank, but it’s another thing altogether to understand the process(es) driving isotopic variation in materials. For example, are the results we observe due to differences in TNT manufacturing process? Or coca plant physiology? Or elephant diet?

Isotope analytical techniques also change over time as better instrumentation is developed. Understanding the impact of different analysis techniques on measured isotope ratios is extremely important when comparisons are made – especially in legal settings. A major focus of the field is the standardization of practices and protocols, to generate comparable results over time and space (e.g., from lab to lab).

How has the need for isotope analysis in forensic investigations changed over the years, if at all?

The forensic application of isotope analysis has been increasing the past 10-20 years. This is partly due to changes in analytical techniques, which have made isotope ratio measurements faster and cheaper. In addition, those who could benefit most from forensic isotope data–law enforcement, regulators, etc.–have become more aware of the technique and it potential usefulness in various types of investigations. We as forensic scientists and isotope analysts can do even more to spread awareness about the technique and its many applications.

Finally, do you have any advice for students hoping to pursue a career in this field of work?

Isotope analysis is one (extremely useful!) tool in a forensic scientist’s toolbox. Having a background and training in other areas–such as anthropology, analytical chemistry, biology, biochemistry, geology, law, or statistics–can be very important when applying isotope analysis techniques and interpreting the resultant data. The field of isotope forensics is relatively small compared to some other forensic disciplines, so be sure to read papers, attend meetings, and network with scientists working in the field.

Visit the Isoforensics Inc. website for more information.

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