Welcome back to Trace Evidence. I am Anupama Raghunathan. Last week we looked at how fingerprints can fail. This week we move to the technique that most people now think of as forensic science itself, DNA. The first time it was ever used in a criminal case, in Leicestershire in 1986, it did something that still surprises my students. It did not catch anyone. It cleared a teenager who had confessed to a murder he did not commit. Only afterwards did police ask more than five thousand men to give blood, and the person responsible was found because he paid a friend to go in his place. We will go through what Alec Jeffreys actually discovered, how a profile is read, and what a modern lab report can and cannot tell a jury. You are listening on Witspeak Podcasts. Let us begin.