At many crime scenes, the only evidence is a bloodstain. Until now, there has been no accurate test to determine the age of the victims and/or perpetrators who left those blood traces. Enter Manfred Kayser and his colleagues from Erasmus MC University, who have discovered a way to estimate the age of people from their blood.
The new method relies on the fact that T cells, immune cells found in blood, produce small circular DNA molecules as a byproduct of their function. However, the amount of these bits of DNA (signal joint T cell receptor excision circles) is not constant. Older individuals have fewer of them, and the decrease occurs at a predictable rate.
Thus far, the method has successfully determined the age of bloodstain donators to within nine years. Although at first this doesn’t sound that accurate, it would give police a great advantage to know whether they were looking for a child, a young adult or a senior citizen.