Brain fingerprinting is an investigative technique that measures brain wave responses to words, phrases or pictures to determine if an individual recognizes specific information related to an event. It involves wearing a headband with sensors to measure EEG signals while being presented relevant and irrelevant stimuli on a computer screen. Brain fingerprinting has four stages - investigation, subject interview, scientific testing, and adjudication - and has proven 100% accurate in over 120 tests, including for the FBI, US intelligence, and US Navy.