The classical methods of forensic science like finger printing, polygraphic lie detector test, narcoanalysis and DNA finger printing are being questioned for their reliability and accuracy. Newer developments in investigating crime are evolving like the use of event related evoked potentials to retrieve the sequence of events of crime as recorded in the brain of the criminal/accused.

The principle of event related evoked potentials is simple. In an oddball paradigm two stimuli of varying characteristics are presented to the individual, one repeated frequently and the other being rare, is given randomly at infrequent intervals. The subject is asked to respond to the infrequent or target stimulus by pressing a button. The response to target stimulus is recorded as P3 wave of the cognitive evoked potentials.

P3 wave of the ERPs has wide applications in cognitive forensic science and interrogative polygraphy in particular. Late vertex positivity in ERP reflects guilt detection in a test known as guilty knowledge. Memory and encoding related multifaceted electroencephalographic responses (MERMER) have been used to determine whether the subject had relevant information (committing of crime) in his brain, after presenting him with probing (relevant), target and non-target stimuli. Two high amplitude P3 waves are recorded in response to target and probing stimuli in case of a knowledgeable person and only one P3 in case of an innocent person.

The newly emerging, late responses to ERP is a step forward to quantify the thought processing feature of the brain. Brain wave science has emerged as a new discipline with promising application in field of crime investigation.

Key words: Event Related Evoked Potentials, MERMER, Target Stimulus, Probing Stimulus. P3 Wave, Long Latency Responses, Lie detection