Isotope analysis
A recent development in forensic science is the isotopic analysis of hair strands. Hair has a recognisable growth rate of 9-11mm per month or 15 cm per year. Human hair growth is primarily a function of diet, especially drinking water intake. The stable isotopic ratios of drinking water are a function of location, and the geology that the water percolates through. Sr, Sr and oxygen isotope variations are different all over the world. These differences in isotopic ratio are then biologically 'set' in our hair as it grows and it has therefore become possible to identify recent geographic histories by the analysis of hair strands. For example, it could be possible to identify whether a terrorist suspect had recently been to a particular location from hair analysis. This hair analysis is a non-invasive method which is becoming very popular in cases that DNA or other traditional means are bringing no answers.
Hair theft
This created a highly profitable market in human hair, which was said in the mid-19th century to be worth twice its weight in silver. In 1851 of hair was imported from France to England with a value of £3,621 (£ today). "The Hairdressers' Journal" reported in May 1863 that a hundred tons of hair a year was being sold in Parisian markets. Not all hair was created equal; female hair from northern Italy and Spain was especially prized for its glossy blackness and curliness. It retailed at a price of 10–12 shillings per ounce (worth about £43/€50/$67 in 2013 prices), rising to £1 per ounce (about £87/€101/$136) for very long hair. A "hair harvest" was held annually in the poorer villages of Italy, where local girls sold their hair to wig-makers. One observer of a hair harvesting event reported seeing "several girls, sheared, one after the other like sheep, and as many more standing ready for the shears, with their caps in their hands, and their long hair combed out, and hanging down to their waists."