The witness on the stand says he saw the accused at the scene of the crime. Is he sure? How sure? The jury’s verdict could hinge on that level of certainty. Many decisions we make every day are influenced by our memories and the confidence we have in them. But very little is known about how we decide whether we can trust a memory or not. Researchers have now identified a unique set of neurons in the medial temporal lobe, an area of the brain where memories and memory-based decisions are processed. They show that the activity of these neurons is indicative of the confidence by which a memory will be retrieved.