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The feasibility of using Event Related Brain Potentials (ERPs) in Interrogative Polygraphy ("Lie Detection") was tested by examining the effectiveness of the Guilty Knowledge Test designed by Farwell and Donchin (1986, 1988). The subject is assigned an arbitrary task requiring discrimination between experimenter-designated targets and other, irrelevant stimuli. A group of diagnostic items ("probes"), which to the unwitting are indistinguishable from the irrelevant items, are embedded among the irrelevant. For subjects who possess "guilty knowledge" these probes are distinct from the irrelevants and are likely to elicit a P300, thus revealing their possessing the special knowledge that allows them to differentiate the probes from the irrelevants. We report two experiments in which this paradigm was tested. In Experiment 1, 20 subjects participated in one of two mock espionage scenarios and were tested for their knowledge of both scenarios. All stimuli consisted of short phrases presented for 300 ms each at an interstimulus interval of 1550 ms. A set of items were designated as "targets" and appeared on 17% of the trials. Probes related to the scenarios also appeared on 17% of the trials. The rest of the items were irrelevants. Subjects responded by pressing one switch following targets, and the other following irrelevants (and, of course, probes). ERPs were recorded from FZ, CZ, and PZ. As predicted, targets elicited large P300s in all subjects. Probes associated with a given scenario elicited a P300 in subjects who participated in that scenario. A bootstrapping method was used to assess the quality of the decision for each subject. The algorithm declared the decision indeterminate in 12.5% of the cases. In all other cases a decision was made. There were no false positives and no false negatives: whenever a determination was made it was accurate. The second experiment was virtually identical to the first, with identical results, except that this time 4 subjects were tested, each of which had a minor brush with the law. Subjects were tested to determine whether they possessed information on their own "crimes." The results were as expected; the Guilty Knowledge Test determined correctly which subject possessed which information. The implications of these data both for the practice of Interrogative Polygraphy and the interpretation of the P300 are discussed.

Brain fingerprinting (BF) detects concealed information stored in the brain by measuring brainwaves. A specific EEG event-related potential, a P300-MERMER, is elicited by stimuli that are significant in the present context. BF detects P300-MERMER responses to words/ pictures relevant to a crime scene, terrorist training, bombmaking knowledge, etc. BF detects information by measuring cognitive information processing. BF does not detect lies, stress, or emotion. BF computes a determination of ''information present'' or ''information absent'' and a statistical confidence for each individual determination. Laboratory and field tests at the FBI, CIA, US Navy and elsewhere have resulted in 0% errors: no false positives and no false negatives. 100% of determinations made were correct. 3% of results have been ''indeterminate.'' BF has been applied in criminal cases and ruled admissible in court. Scientific standards for BF tests are discussed. Meeting the BF scientific standards is necessary for accuracy and validity. Alternative techniques that failed to meet the BF scientific standards produced low accuracy and susceptibility to countermeasures. BF is highly resistant to countermeasures. No one has beaten a BF test with countermeasures, despite a $100,000 reward for doing so. Principles of applying BF in the laboratory and the field are discussed.

This experiment examined the accuracy and reliability of the memory and encoding related multifaceted electroencephalographic response (MERMER) technique for detecting information related to events subjects have experienced, despite subjects' efforts to conceal that knowledge. Information obtained through interviews was used to develop stimulus sets consisting of words and phrases presented to subjects visually by computer. Sets were composed of three types of stimuli: life experience-related (Probes), stimuli the subject was asked to memorize and respond to (Targets), and irrelevant information (Irrelevants). Each set of stimuli was tested on two individuals: (1) one individual who had participated in the event in question—and thus had the relevant information stored in his/her brain, and (2) one who had not. Six subjects were tested. Electrical brain responses to the stimuli were recorded non-invasively from the scalp and analyzed. MERMERs, (memory and encoding related multifaceted electroencephalographic responses), of which the P300 is a sub-component, were used to determine whether the subject had the relevant information stored in his brain (information present) or not (information absent), thus indicating whether or not each subject had participated in the real-life event in question. Bootstrapping was used to analyze and compare the responses to the three types of stimuli. As predicted, MERMERs were elicited by Probe stimuli only in the subjects who had participated in the investigated event, by Target stimuli in all subjects, and in no case by Irrelevant stimuli. For each of the six subjects, brain MERMER testing correctly determined whether the subject had participated in and consequently knew about the event in question (information present) or had not participated (information absent). The statistical confidence for this determination was 99.9% in five cases and 90.0% in one case. The article concludes with a discussion of areas of future research and the potential for using this new technology as an investigative tool in criminal cases.

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