The `Brain Electrical Activation Profile test’, also known as the `P300 Waves test‘. It is a process of detecting whether an individual is familiar with certain information by way of measuring activity in the brain that is triggered by exposure to selected stimuli. This test consists of examining and measuring `event-related potentials’ (ERP) i.e. electrical wave forms emitted by the brain after it has absorbed an external event.

An ERP measurement is the recognition of specific patterns of electrical brain activity in a subject that are indicative of certain cognitive mental activities that occur when a person is exposed to a stimulus in the form of an image or a concept expressed in words. The measurement of the cognitive brain activity allows the examiner to ascertain whether the subject recognised stimuli to which he/she was exposed. [1]

The evaluation

By the late 19th century it had been established that the brain functioned by emitting electrical impulses and the technology to measure them was developed in the form of the electroencephalograph (EEG) which is now commonly used in the medical field. Brain wave patterns observed through an EEG scan are fairly crude and may reflect a variety of unrelated brain activity functions.

It was only with the development of computers that it became possible to sort out specific wave components on an EEG and identify the correlation between the waves and specific stimuli. The P300 wave is one such component that was discovered by Dr. Samuel Sutton in 1965. It is a specific event-related brain potential (ERP) which is triggered when information relating to a specific event is recognised by the brain as being significant or surprising.

The P300 waves test

The P300 waves test is conducted by attaching electrodes to the scalp of the subject, which measure the emission of the said wave components. The test needs to be conducted in an insulated and air-conditioned room in order to prevent distortions arising out of weather conditions. Much like the narcoanalysis technique and polygraph examination, this test also requires effective collaboration between the investigators and the examiner, most importantly for designing the stimuli which are called `probes’.

Ascertaining the subject’s familiarity with the `probes’ can help in detecting deception or to gather useful information. The test subject is exposed to auditory or visual stimuli (words, sounds, pictures, videos) that are relevant to the facts being investigated alongside other irrelevant words and pictures. Such stimuli can be broadly classified as material `probes’ and neutral `probes’.

The underlying theory is that in the case of guilty suspects, the exposure to the material probes will lead to the emission of P300 wave components which will be duly recorded by the instruments. By examining the records of these wave components the examiner can make inferences about the individual’s familiarity with the information related to the crime.[2]

Brain Fingerprinting

The P300 wave test was the precursor to other neuroscientific techniques such as `Brain Fingerprinting’ developed by Dr. Lawrence Farwell. The latter technique has been promoted in the context of criminal justice. There is an important difference between the `P300 waves test’ that has been used by Forensic Science Laboratories in India and the `Brain Fingerprinting’ technique.

Dr. Lawrence Farwell has argued that the P300 wave component is not an isolated sensory brain effect but it is part of a longer response that continues to take place after the initial P300 stimulus has occurred. This extended response bears a correlation with the cognitive processing that takes place slightly beyond the P300 wave and continues in the range of 300-800 milliseconds after the exposure to the stimulus.

This extended brain wave component has been named as the MERMER (Memory-and Encoding-Related-Multifaceted-Electroencephalographic Response) effect[3].

Limitations of P300 in Criminal Justice System

Even though the P300 Wave component has been the subject of considerable research, its uses in the criminal justice system have not received much scholarly attention. Dr. Lawrence Farwell’s `Brain Fingerprinting’ technique has attracted considerable publicity but has not been the subject of any rigorous independent study.

Besides this preliminary doubt, an important objection is centred on the inherent difficulty of designing the appropriate `probes for the test. Even if the `probes are prepared by an examiner who is thoroughly familiar with all aspects of the facts being investigated, there is always a chance that a subject may have had prior exposure to the material probes.

In case of such prior exposure, even if the subject is found to be familiar with the probes, the same will be meaningless in the overall context of the investigation. For example, in the aftermath of crimes that receive considerable media-attention the subject can be exposed to the test stimuli in many ways. Such exposure could occur by way of reading about the crime in newspapers or magazines, watching television, listening to the radio or by word of mouth.

A possibility of prior exposure to the stimuli may also arise if the investigators unintentionally reveal crucial facts about the crime to the subject before conducting the test. The subject could also be familiar with the content of the material probes for several other reasons.

Another significant limitation is that even if the tests demonstrate familiarity with the material probes, there is no conclusive guidance about the actual nature of the subject’s involvement in the crime being investigated. For instance, a by- stander who witnessed a murder or robbery could potentially be implicated as an accused if the test reveals that the said person was familiar with the information related to the same.

Furthermore, in cases of amnesia or `memory-hardening’ on part of the subject, the tests could be blatantly misleading. Even if the inferences drawn from the `P300 wave test’ are used for corroborating other evidence, they could have a material bearing on a finding of guilt or innocence despite being based on an uncertain premise.

Admissibility in Law

An unresolved question is whether the results obtained through BEAP Test, is of a testimonial nature. In this test, inferences are drawn from the physiological responses of the subject and no direct reliance is placed on verbal responses. In some forms of BEAP examination, the subject may be required to offer verbal answers such as `Yes’ or `No’, but the results are based on the measurement of changes in several physiological characteristics rather than these verbal responses.

In India, the Supreme court, considered the question of its admissibility in detail in the case of ‘Selvi v. State of Karnataka, (2010)’.

While concluding the judgment, the court held-

  • The compulsory administration of the test violates the `right against self- incrimination’. This is because the underlying rationale of the said right is to ensure the reliability as well as voluntariness of statements that are admitted as evidence. Supreme Court has recognised that the protective scope of Article 20(3) extends to the investigative stage in criminal cases and when read with Section 161(2) of the Code of Criminal Procedure, 1973 it protects accused persons, suspects as well as witnesses who are examined during an investigation.

The test results cannot be admitted in evidence if they have been obtained through the use of compulsion.

  • Article 20(3) protects an individual’s choice between speaking and remaining silent, irrespective of whether the subsequent testimony proves to be inculpatory or exculpatory.
  • Forcing an individual to undergo the test violates the standard of `substantive due process’ which is required for restraining personal liberty. Such a violation will occur irrespective of whether these techniques are forcibly administered during the course of an investigation or for any other purpose since the test results could also expose a person to adverse consequences of a non-penal nature.
  • The compulsory administration of technique is an unjustified intrusion into the mental privacy of an individual. It would also amount to `cruel, inhuman or degrading treatment’ with regard to the language of evolving international human rights norms.
  • Furthermore, placing reliance on the results gathered from this test comes into conflict with the `right to fair trial’. Invocations of a compelling public interest cannot justify the dilution of constitutional rights such as the `right against self-incrimination’.
  • No individual should be forcibly subjected to test in question, whether in the context of investigation in criminal cases or otherwise. Doing so would amount to an unwarranted intrusion into personal liberty.
  • However, the court left room for the voluntary administration of the test in the context of criminal justice, provided that certain safeguards are in place.
  • Even when the subject has given consent to undergo test, the test results by themselves cannot be admitted as evidence because the subject does not exercise conscious control over the responses during the administration of the test.
  • However, any information or material that is subsequently discovered with the help of voluntary administered test results can be admitted, in accordance with Section 27 of the Evidence Act, 1872.
  • THE NATIONAL HUMAN RIGHTS COMMISSION HAD PUBLISHED `GUIDELINES FOR THE ADMINISTRATION OF POLYGRAPH TEST (LIE DETECTOR TEST) ON AN ACCUSED’ IN 2000. These guidelines should be strictly adhered to and similar safeguards should be adopted for conducting the `BEAP  technique’.

The text of these guidelines has been reproduced below:

(i) No Lie Detector Tests should be administered except on the basis of consent of the accused. An option should be given to the accused whether he wishes to avail such test.

(ii) If the accused volunteers for a Lie Detector Test, he should be given access to a lawyer and the physical, emotional and legal implication of such a test should be explained to him by the police and his lawyer.

(iii) The consent should be recorded before a Judicial Magistrate.

(iv) During the hearing before the Magistrate, the person alleged to have agreed should be duly represented by a lawyer.

(v) At the hearing, the person in question should also be told in clear terms that the statement that is made shall not be a `confessional’ statement to the Magistrate but will have the status of a statement made to the police.

(vi) The Magistrate shall consider all factors relating to the detention including the length of detention and the nature of the interrogation.

(vii) The actual recording of the Lie Detector Test shall be done by an independent agency (such as a hospital) and conducted in the presence of a lawyer.

(viii) A full medical and factual narration of the manner of the information received must be taken on record.


Selvi v. State of Karnataka, (2010)

(Reference in the article, as quoted by court in the judgment)

[1] Andre A Moenssens, `Brain Fingerprinting – Can it be used to detect the innocence of persons charged with a crime?’ 70 University of Missouri at Kansas City Law Review 891-920 (Summer 2002) at p. 893

[2] Laboratory Procedure Manual – Brain Electrical Activation Profile (Directorate of Forensic Science, Ministry of Home Affairs, Government of India, New Delhi – 2005)

[3] Lawrence A. Farwell, `Brain Fingerprinting: A new paradigm in criminal investigations and counter-terrorism’, (2001)