DETECTION OF DECEPTION BY BRAIN FINGERPRINTING

With the increasing crime rate in today’s world investigators have started using some scientific techniques to gather more information for criminal investigation. These techniques are popularly known as Deception Detection Techniques. Polygraph, Narco Analysis and Brain fingerprinting techniques come under this category. These techniques have been found to be very helpful in taking out the concealed information, or facts related to case. It gives further lead to the investigator to solve the case.

BRAIN FINGERPRINTING

This technique was developed by Dr. Lawrence A. farwell in 1995. The theory behind this technique is that the brain is involved in every act, be it planning for an event, execution of an event. So, this way brain can be used to reveal that concealed or hidden information by this technique.

Principle –

It is an objective, scientific and psychophysiological method used for gathering information related to the crime by measuring brain waves responses to particular stimuli presented to the subject (the one going through the Brain fingerprinting test). Brain fingerprinting uses electroencephalography to measure brain responses to measure event related potentials known as P300 (electrical brain response occur after 300 milliseconds of presenting a stimuli). This technique involves presenting certain pictures, phrases or words that are somehow relevant to the crime scene with some irrelevant stimuli also on a computer screen. This test can only be applied when the investigator knows some specific information about the crime.

Instrumentation-

The devices used in the brain fingerprinting system are as follows-

i) A personal computer

ii) Data aquistion board

iii) A graphic card for driving two monitors from one PC

iv) Four channeled EEG amplifier system

v) Software for data acquisition and analysis

The entire system is computer control from presentation of stimuli and recording of brain waves responses and mathematical data analysis algorithm for comparison of three types of stimuli (probe, target and irrelevant). The test gives results if the information is present as ‘guilty’ and in absence of information as ‘innocent’.

Working –

Once the Sensors on a headband are placed on the subject ‘s head the stimulus are shown on a monitor in the form of a picture for a fraction of second (1800ms) and a simpler stimulus like a word or phrase is shown for a shorter period. The subject is first shown the target and irrelevant stimuli to get the reference waveform. Probe stimuli is then presented to the subject which generates P300-MERMER (memory and encoded related multifaceted electroencephalographic response) in subject’s brain. Multiple stimulus are shown and data is processed. For each repetition of stimulus the probe, target and irrelevant waveform are compared.

Technique-

Brain fingerprinting uses the basic fact that the brain produces certain signals or waves when presented to some stimuli after 300 milliseconds (known as P300). So, following kinds of stimuli are presented to a subject in this technique-

i) Probe stimuli – the probe test is used to tell if the subject has the knowledge regarding the crime and these probes are always related to the criminal activity.

ii) Target stimuli- It provides the reference signal waveform for comparing with the probe stimuli. Target stimuli contains information relevant to the situation that is known to the subject. Target stimuli
contains information that has been revealed to the subject after the crime or investigated situation.

iii) Irrelevant stimuli- it contains no relevant information related to crime or the subject.

Conclusion-

Brain fingerprinting has proved to be a very powerful technique and has helped in solving out cases yet, it acts as a corroborative evidence. The Supreme Court of India rules out that this deception detection technique can only be used with the consent of the subject and under supervision. So, basically this technique provides aid in criminal investigation. However, having many advantages a few limitations of this technique are also there. It can’t be used in every case as its set up is costly. Sometimes may be an eye witness of a case can also have knowledge regarding a crime just like any culprit. So, this scientific evidence can only be of a corroborative value.