You can see how the same observation can be "consistent with" different stories. It is for that reason that the phrase, beloved of crime writers, is not very useful in real crime investigation. It merely means that the story being offered is one of the possibilities. The real job is to evaluate which of the possibilities is the best fit to all of the observations, not just those that fit what you think or wish.

X-rays are a recent development in historical terms and can be used by modern investigators to look at injuries to bones. Even breaks or fractures suffered years before can often be seen by radiographers. They can also sometimes identify victims of accidents or homicide, or sometimes match damage caused by surgery or extraction of teeth to medical records of victims.

In these instances radiography is used by osteologists (who study bones), and odontologists (who study teeth). Some forensic odontologists also claim to be able to identify the person who made a bite mark. Bite marks are sometimes found on the body of a victim of some kind of abuse, or even in items found at crime scenes such as cheese sandwiches or apples. In Otzi’s case, the findings were a bit more mundane. An arrowhead and part of the shaft were found embedded in his shoulder. This may be evidence of an attack, or maybe a hunting accident? These techniques have been around for a few years now, but some fairly modern scientific analyses used nowadays in forensic science have provided further clues about Otzi.

The elements that are all around us, such as oxygen, nitrogen, carbon, and iron, are present in subtly different forms. These forms all behave exactly the same in their reactions with other chemicals as they form new ones such as carbon dioxide, water, and indeed all the chemicals that make you. However, a technique called isotopic analysis can tell the different forms apart. It’s called isotopic analysis because the different forms are called isotopes (the prefix ‘iso’ means ‘the same’; e.g. isobars, isotherms, isotonic). If you really must know, the difference between the forms is the number of neutrons in the nucleus of the atoms of the element. That may come in useful in your next pub quiz – maybe it’ll be a half a million pound question one day.

What makes them interesting is that the different isotopes are present in different ratios at different times and different places. The technique of radiocarbon dating uses the ratios of the isotopes of carbon to date fossils to the nearest few thousand years – so it’s not very accurate as a watch. Isotopic analysis of Otzi’s tooth enamel, and comparisons with samples from surrounding areas, showed that he had spent his childhood in the area in which he was found (the Eisack Valley in the South Tyrol, Italy) but that he spent his adulthood in Lower Vinschgau, also in the Tyrol.

Forensic isotopic analysis is now being applied to such things as adhesives, packaging materials, drugs, bullets, and even safety matches. Recently, police have used the technique to try to discover something about the history of an abandoned baby found in Edinburgh. They believe on the basis of the technique that the mother recently arrived in the UK from Eastern Europe. Time may tell if they are right.

In attempting to sort out the good stories from the bad, it is not always obvious which evidence to believe. Different types of evidence can appear to contradict each other; Otzi’s arrows are claimed as evidence that he spent his time hunting at high altitude whereas the geological isotopic evidence suggests otherwise. There is no magic formula for working all of this out. The best that the scientists can do is give possible stories and some estimate of how confident they are in those stories. There is one exception; exclusion. If, for example, your DNA or fingerprint does not match the DNA of the perpetrator found at the crime scene then we are sure that you are not amongst the suspects.

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Content last updated: 10/01/2006

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