Brain Fingerprinting is a forensic technique that uses brain-reading techniques to determine whether specific information is stored in a subject’s brain. It does this by measuring electrical brainwave responses to words, phrases, or pictures that are presented on a computer screen.
Brain fingerprinting was invented by Lawrence Farwell. It is based on the theory that the brain processes the known and the relevant information differently from the way it processes unknown or irrelevant information. The brain’s processing of known information, such as the details of a crime stored in the brain, is revealed by a specific pattern in an EEG (electroencephalograph).
The technique uses the well known fact that an electrical signal known as P300 is emitted from an individual’s brain beginning approximately 300 milliseconds after it is confronted with a stimulus of special significance, e.g. a rare vs. a common stimulus or a stimulus the subject is asked to count. The application of this in brain fingerprinting is to detect the P300 as a response to stimuli related to the crime or other investigated situation, e.g., a murder weapon, victim’s face, or knowledge of the internal workings of a terrorist cell.
- Because it is based on EEG signals, the system does not require the subject to issue verbal responses to questions or stimuli.
- Since brain fingerprinting uses cognitive brain responses, brain fingerprinting does not depend on the emotions of the subject, nor is it affected by emotional responses.
- Brain fingerprinting is fundamentally different from the polygraph (lie-detector), which measures emotion-based physiological signals such as heart rate, sweating, and blood pressure. [For details, kindly see Topic No. 294 “Polygraph Test”]
- Also, unlike polygraph testing, it does not attempt to determine whether or not the subject is lying or telling the truth. Rather, it measures the subject’s brain response to relevant words, phrases, or pictures to detect whether or not the relevant information is stored in the subject’s brain.
Brain fingerprinting has been applied in a number of high-profile criminal cases and has been ruled admissible in courts in the US where it originated. In India, in the controversial Sister Abhaya murder case, the Ernakulam Chief Judicial Magistrate court had asked the CBI to make use of all modern investigation techniques, including brain fingerprinting.
Brain fingerprinting is a controversial technique. It has been criticized on a number of fronts. Some of its limitations are:
- Brain fingerprinting does not detect lies. It simply detects information. It does not detect how that information got there. This fact has implications for how and when the technique can be applied.
- Brain fingerprinting detects only information, and not intent. It is not applicable where a suspect and an alleged victim agree on the details of what was said and done, but disagree on the intent of the parties.
- Brain fingerprinting does not determine whether a suspect is guilty or innocent of a crime.
- In structuring a brain fingerprinting test, the technician must avoid including information that has been made public. Detecting that a suspect knows information he already obtained by reading a newspaper would not be of use in a criminal investigation and may result in wrong incrimination.
- Another situation where brain fingerprinting is not applicable is one where the authorities have no information about what crime may have taken place.