Brain fingerprinting is a technique that detects whether specific information is stored in a person's brain. It works by presenting stimuli related to a crime or event and measuring brainwave responses, particularly the P300 response. If the P300 response is elicited, it suggests the person has knowledge of the event stored in their memory. The technique has potential applications in criminal investigations to identify criminals and exonerate the innocent. However, it also has limitations and requires more research.