An isotopic analysis of one's hair can reveal where a person drank water, according to a study published in Proceedings of the National Academy of Sciences by Thure Cerling of the University of Utah and colleagues. The discovery could help forensic scientists track the past movements of criminal suspects or unidentified murder victims. "You are what you eat and drink - and that is recorded in your hair," explains geochemist Cerling, who worked with ecologist Jim Ehleringer on the study. "We have found significant variations in hydrogen and oxygen isotopes in hair and water that relate to where a person lives in the United States," Ehleringer adds, "Police are already using this to reconstruct the possible origins of unidentified murder victims." Their new approach to hair analysis may also prove useful to anthropologists, archaeologists and in medicine.