Researchers at the Erasmus MC University in Rotterdam have invented a method to estimate the age of an unknown person from just one drop of blood originating from that person. The estimated age can be an important clue in tracking down the perpetrator of a crime or in identifying the victims of disasters. The lead researcher, Manfred Kayser, professor of Forensic Molecular Biology at Erasmus MC remarked, "We used the observation that certain DNA molecules in some blood cells decrease with age. Based on this, we developed a reliable and sensitive, but simple test enabling prediction of the age category of the person from whom the blood droplet originated. We are now trying to make the age determination using a drop of blood more accurate." The original scientific article Estimating human age from T-cell DNA rearrangements was published in Current Biology and is available here.