Legend says soil analysis technique dates back to Roman soldiers

Dr Raymond Murray said the first investigative use of soil analysis by the US Federal Bureau of Investigation was in 1935. But if there is truth in the legend, the FBI was preceded by quite a few centuries by the ancient Romans, who used to look at the soil under enemies' horses in an attempt to guess at their previous whereabouts.

The history of soil as an investigative tool has, appropriately, its muddy areas - but dig around and an interesting narrative unfolds. In the mid-19th century in Germany, a soil sample provided the breakthrough in a case of large-scale theft, Dr Murray recounted. A large amount of silver was being shipped via railroad.But when the box containing the precious metal was opened at its destination, it was empty except for traces of dirt.

That, however, proved sufficient for the mineralogist who was called to examine the soil. He pinpointed where along the train's route the theft took place and the perpetrators were eventually found. But it was not until the early 1900s that soil evidence got its big breakthrough. A German forensic scientist, Georg Popp, solved two murders in 1904 and 1908 with the help of soil samples that proved the suspects had been at the crime scenes.

In the 1908 case, Mr Popp was even able to restore the sequence of events - with the suspect walking away from his house, to the murder scene and to another location where he discarded some personal belongings - by separating three layers of soil which had accumulated atop one another on the soles of his shoes. Increasingly, geologists are proving useful to intelligence services, too. This is the case with the scientist John Shroder, who, from studying a rock outcropping shown in video foorage, was able to identify the region where Osama bin Laden was at the time he made a speech in 2001.

Dr Murray has seen great change since he started as a forensic geologist. "We have publicised the value of this evidence and you see many more cases today than you could see 30 years ago," he said. "As with any evidence, someone must collect it or it will never be studied. Many more people are studying the samples now." @Email:[e-mail]