Using isotopes found in hair to solve cold cases

OpenLab

Gazette
published: Sept 21

Michelle Chartrand and Gilles St-Jean

The Scientists

In 2001, the skeletal remains of a woman were discovered in downtown Montreal. The corpse, dubbed Madame Victoria, had lain undiscovered near the Royal Victoria Hospital for two years. Police had nowhere to start and the case went cold.

Five years later, the RCMP invited University of Ottawa professor Gilles St-Jean to suggest ways his research on stable isotopes could help forensic science. The force was excited about the possibilities, and decided to run a pilot project. St-Jean hired post-doctoral researcher Michelle Chartrand to apply isotope mass spectrometry and help law enforcement officials. After five years of work, St-Jean and Chartrand can now determine where people (even those like Madame Victoria whose corpses have decayed over a decade) have recently been, thanks to isotope analysis.

The Science

The food we eat and the water we drink is made up of atoms, atoms that come in different flavours, known as isotopes. Isotopes are atoms of the same element but with different mass. For instance, hydrogen has two stable isotopes (common hydrogen-1 and rare hydrogen-2), while oxygen has three (common oxygen-16, rare oxygen-18 and -17). Isotopes become incorporated in our bodies though our diets and the water we drink.

This means that analyzing the stable isotopes in tissue can tell investigators all sorts of interesting things. For example, vegetarians are easy to spot through analysis of nitrogen, while North Americans, with their different diet, are easily distinguished from Europeans through carbon signals.

Most importantly for criminal investigations, stable isotope analysis can reveal differences of location. Isotope presence isn’t the same everywhere. Water found in different regions has different isotope content. St-Jean and Chartrand can measure the ratio of isotopes found in a person’s tissue, compare it to a reference and determine if there is a match.

Even better, a person’s hair offers more information than ordinary tissue. Since it grows at about 1 cm per month, hair acts as an archive that records location over time and potentially provides police with years worth of information.

The Solution

Three years ago, all this this forensic power was useless. To actually figure out where a person was from required a database mapping out isotope ratios across the country.

So Chartrand and undergraduate researcher Jonathan Mayo jumped in a car and spent four years driving over 40,000 km across Canada building a detailed map of isotopes.

Armed with their invaluable map, St-Jean and Chartrand solved the police’s quandary: Madame Victoria had lived in seven separate locations in the three-and-a-half years prior to her death. She began in northern Ontario or Quebec and moved southward, stopping intermittently until she arrived in Montreal.  And none of this could have been known without the forensic power of isotope analysis developed at uOttawa.

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