Forensics: Stable Isotope Profiling

Aug 5, 2013 - by Liz Porter - 0 Comments

Aug. 5, 2013

The latest big thing in forensics is a technique called “stable isotope analysis,” a process that allows scientists to analyze a human body’s hair – or fingernails or bones – to find out where its owner has been living or travelling.             

by Liz Porter

In November 2006, a badly beaten man of Asian appearance was dumped at the accident and emergency section of a hospital in the Welsh county of Gwent, in the UK.  The victim died shortly afterwards, without ever speaking. So police were desperate to discover who he was – and why he had been attacked.

Frustratingly, none of the usual modern forensic methods could help. Neither the man’s fingerprints nor his DNA profile matched any UK records. If he had been a recent arrival, there should have been a record of him entering the country, but there wasn’t.

But police had one last forensic tool at its disposal: a 21st century technique hailed as “the next big thing” after DNA and known as “stable isotope profiling” or “stable isotope ratio analysis.”

This technique involves scientists analyzing a human body’s hair – or fingernails or bones – to find out where its owner has been living or travelling. Often summarized as “you are what you eat and drink – and where you eat and drink,” stable isotope profiling is based on two key facts. The first is that our hair and bones show traces of the water we have ingested in food and drink. The second is that water sources from different geographical areas can be chemically distinguished from one another.

All water is the same in the sense that each molecule is composed of two atoms of hydrogen and one of oxygen. But different water sources contain subtly varying concentrations of hydrogen and oxygen isotopes (forms of the same chemical element with a different atomic weight). So the water from one area has a subtly different “isotope signature” from water sampled in another – and this “signature” can be detected in human hair, bones and fingernails.

A Gwent police crime scene investigator snipped 145 millimeters of hair from the mystery murder victim’s scalp: a length that represented 14 and half months of growth. She then took it the Stable Isotope Forensics laboratory at Dundee’s James Hutton Institute.  There, using an isotope ratio mass spectrometer – a $400,000 apparatus that records the ratios of particular isotopes in different samples of material, scientist Dr. Wolfram Meier-Augenstein was able to trace the dead man’s movements.

The dead man’s hair “told” the scientist that its owner had spent 2.5-3 months in the Ukraine, had moved to   Germany for 6 -7 months and then to Wales, where he spent the last 2.5 months of his life.

Germany proved to be the key clue because the German police’s fingerprint data base was able to provide a match for the dead man’s prints.  It identified him as Vietnamese-national Tran Nyugen, who had been transported illegally into the UK by a people- smuggling gang that had forced him to work as a cannabis farmer to pay off his travel debts of £30,000. Unfortunately, Tran Nyugen’s crop was stolen by a rival gang and the gang who smuggled him into the UK kidnapped and tortured him in an attempt to get information about its rivals. Three men were found guilty of his murder in 2008.

In 2005 Dr. Meier-Augenstein was able to use stable isotope profiling to help Dublin Police after the dismembered and headless body of a black man was found in Dublin's Royal Canal. Using stable isotope profiling on bones, hair and fingernails, the forensic scientist, then based in Belfast, was able to identify the Horn of Africa as the victim's most likely birthplace. He could also tell police that the man had entered Ireland about six years before his death. Inquiries in Dublin's African community yielded a possible identity, which was then confirmed by DNA. The dead man was Kenyan Farah Swaleh Noor, boyfriend of local woman Kathleen Mulhall. In 2006, Mulhall's daughters, Charlotte and Linda (dubbed the "Scissor Sisters"), were convicted, one of murder, the other of manslaughter, for bludgeoning Noor to death and cutting up his body.

Sadly, the first UK police investigation to use stable isotope profiling remains unsolved. This is the case of “baby Carrie,” the murdered newborn baby girl whose body was dumped in a black bin bag on the outskirts of the Northern Irish village of Carryduff in 2002.

After obtaining the mystery baby's profile, DNA testing 1,300 local girls and women and drawing a blank, local police turned to Dr. Meier-Augenstein. Measuring the ratios of hydrogen and oxygen isotopes in the baby's hair and bones, the scientist compared them to the corresponding ratios found in the water around Ireland and Europe. He was then able to tell the homicide detectives that the mother was not a local(by pulley). In fact, she had been living in a different part of Europe altogether. He could even give police an estimate of her time of arrival in Northern Ireland. But the case stalled there, with police continuing to make appeals for fresh information every few years.

In late 2007, five years after the brutal murder of seamstress Heather Barnett in the UK city of Bournemouth, stable isotope profiling produced an intriguing clue. University of Reading archaeology lecturer Dr. Stuart Black analyzed cut hair that had been found in the victim’s hand. His work on the nine-centimeter strands revealed that the hair’s owner lived in Britain, but had visited either eastern Spain or southern France 11 weeks before the hair was cut, for up to six days. The person had also visited Tampa, Florida, for eight days, two and a half weeks before the hair was cut. This information never enabled police to trace its owner but it helped confirm the profile of the killer as a hair fetishist who had been known to covertly clipped the hair of women on buses in both Italy and the UK.

In 2008 researchers from the University of Utah had confirmed that hydrogen and isotope variations in people's hair could be used to trace their travels from state to state around the United States. Their work was then used to reconstruct the final two years in the life of an unidentified murder victim found near Salt Lake City in 2000.  The remains of the woman, then known as “Saltair Sally” had been found by duck hunters just near the Great Salk Lake.

The researchers determined that the woman had traveled in Idaho, Washington and Oregon in the last two years of her life: information that helped investigators sort through the many missing persons who matched the woman's description. Finally in August 2012, the woman was identified as Nikole Bakoles, 20, whose family had lost touch with her before 2000 and had not reported her missing until 2003.

Scientists also use isotope profiling to find the subtly different isotope signatures of different batches of illicit drugs, and of bomb ingredients sourced from different countries. Isotope analysis, along with the analysis of trace elements from soil, can also be used as a means of verifying the origins of foodstuffs and drugs.

Interestingly, while stable isotope ratio analysis has only been used by police in the 21st century, it has been used by archaeologists since the early 1980s, with researchers analyzing the isotope ratios of different elements, including carbon, nitrogen and sulfur, within skeletons and mummies, and then drawing conclusions about the diets of ancient populations. In 2007, researchers analyzed hair samples from naturally preserved child mummies unearthed at an archaeological site in the Andes. Their results supported a theory that the children had been fattened up for sacrifice. The analysis indicated that the children had been raised on a vegetable diet, but, in the 12 months before their deaths, there was an indication of a change, to a diet enriched with foods regarded as “elite,” such as maize, and protein, possibly from charqui (dried llama meat). Stable isotope ratio analysis on hair may also one day be able to reveal whether ancient Egyptian mummies found together came from the same area.

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