DNA samples are generally matched using a minimum of 6 genetic markers that are present in both samples. One sample for example may be taken from crime scene evidence and matched to samples in a data base. Now, a team of scientists has been working on a mathematical algorithm that can match DNA with just half the makers. So, three instead of six. That means it can match partial or degraded DNA samples. Dr Francois-Xavier Laurent, from the Interpol DNA unit in France spoke to Lisa Owen.