Brain fingerprinting
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Brain fingerprinting is a technique that measures recognition of familiar stimuli by measuring electrical brain wave responses to words, phrases, or pictures that are presented on a computer screen. Brain fingerprinting was invented by Dr. B. S. Farwell. The theory is that the suspect's reaction to the details of an event or activity will reflect if the suspect had prior knowledge of the event or activity. This test uses the Memory and Encoding Related Multifaceted Electroencephalographic Response to detect familiarity reaction. It is hoped it might be more accurate than a polygraph (lie-detector) test, which measures physiological signals such as heart rate, sweating, and blood pressure.
The person to be tested wears a special headband with electronic sensors that measure the EEG from several locations on the scalp. In order to calibrate the brain fingerprinting system, the testee is first presented with a series of irrelevant stimuli, words, and pictures, and then a series of relevant stimuli, words, and pictures. The testee’s brain response to these two different types of stimuli allow the testor to determine if the measured brain responses to test stimuli, called probes, are more similar to the relevant or irrelevant responses.
The technique uses the fact that an electrical signal known as P300 is emitted from an individuals brain exactly 300 milliseconds after it is confronted with a stimulus that has special significance to that individual (e.g. a murder weapon or a victim's face). Because it is based on EEG signals, the system does not require the testee to issue verbal responses to questions or stimuli. Also, unlike polygraph testing, it does not attempt to determine whether or not the testee is lying or telling the truth. Rather, it attempts to measure the testee’s brain response to a record of relevant words, phrases, or pictures.
Background and terminology
"Brain fingerprinting" is a portable test that is advertised to be able to discover, document, and provide evidence of guilt, affectedness by marketing, and identify members of dormant terrorist cells. This is primarily a discussion of the Dr. Larry Farwell's paper, “Using Brain MERMER Testing to Detect Concealed Knowledge Despite Efforts to Conceal” [1], published in the Journal of Forensic Sciences in 2001 by Dr. Farwell and FBI Special Agent Ms. Smith of the FBI. This paper describes a test of brain fingerprinting, a technology based on EEG that is purported to be able to detect the existence of prior knowledge or memory in the brain. The P300 occurs when the tested subject is presented with a rarely occurring stimulus that they feel is significant. When an irrelevant stimulus is presented, a P300 is not expected to occur. The P300 is widely known in the scientific community, and is also known as an Oddball-evoked P300. A similar response occurs in as a P600 or N400 during syntactic or semantic processing and is elicited by inappropriate words or strange grammar structures. The main goal of Farwell's brain fingerprinting tests upon deceptive subjects is to prove that the perceptions and goals of the subject upon their non-cognitive brain processes has zero effect upon the efficacy of the MERMER test.
While researching the P300, the author of this paper, Dr. Farwell, created a more detailed test that not only included the P300, but also observes the stimulus response up to 800ms after the stimulus. He calls this technique a MERMER, memory and encoding related multifaceted electroencephalographic response. This P300, an electrically positive component, maximal at the midline parietal area of the head, has a peak latency of approximately 300 to 800 ms. The MERMER s an electrically negative component, maximal at the midline frontal area, with an onset latency of approximately 800-1200ms.
Criticisms
Some believe brain fingerprinting needs far more refinement before its use becomes widespread and court cases are decided on its evidence. A large proportion of the scientific community believes that this new test will have the same limitations as the older polygraph test. Several studies have shown it is possible to control electroencephalographic response in much the same way as it is possible to fool a polygraph test; however, a higher level of training and discipline is required.
For the longest time, neither American or European courts admitted "brain fingerprints" as evidence. Although in March 2002, Iowa District Court Judge Tim O'Grady allowed for Brain Fingerprinting test to be accepted as evidence in a petition filed for Terry Harrington, who was serving a life sentence for a 1977 murder.
Ethical considerations
Farwell ignores the ethical considerations of the ability to interpret someone’s mind to test if they possess specific knowledge. The designers and supporters of brain fingerprinting do not seem concerned with the unethical uses of this technology, and have made it clear that this test is designed for, and created with the aid of, government agencies. Some feel that a discussion of the humanitarian use in reducing stress for innocent people that are accused is unethical when the ethics of the technology itself is not discussed.
Current uses and research
It has been tentatively used by the FBI to test for recognition of crime scenes in hope of proving guilt. It is not admissible in court.
Dr. Farwell also proposes the use of this test for airport screening and other forms of routine employment, military, and foreign intelligence screening. However, clearly, one cannot make such proposals based on such small sample sizes with such rigorously controlled stimulus and response mechanisms in a contrived environment.
Jimmy Ray Slaughter was convicted in 1991 of the murder of his former girlfriend and their eleven month old daughter. In February 2004, Dr. Farwell ran the brain fingerprinting testing on Slaughter and showed he did not know several prominent facts of the crime scene. "Jimmy Ray Slaughter did not know where in the house the murder took place; he didn't know where the mother's body was lying or what was on her clothing at the time of death — a salient fact in the case," says Dr Farwell. Jimmy Ray Slaughter was executed by the state of Oklahoma on March 15, 2005.
Research into brain fingerprinting is currently being funded by the CIA. Its use has been touted as a means of intelligence gathering to prevent terrorism.
Farwell's MERMER system is not, and has been proven to have any more accuracy than chance, and is only valid under extremely controlled and contrived circumstances. While new forms of lie detection are currently under development, these are generally based on fMRI, PET, and are based on events in the prefrontal cortex. Currently fMRI evidence of ability to perform moral reasoning before the age of 18 is being considered as evidence in a case by the United States Supreme Court. Farwell's MERMER has been accepted as evidence in the Iowa Supreme Court on two occasions.
External links
- Dr.Farwell's Brain Fingerprinting Laboratories website
- Discussion of legal and scientific critiques of Farwell's theories
- Simple, Effective Countermeasures to P300-based Tests of Detection of Concealed Information (PDF)
- "It's the thought that counts for the guilty", The Observer, April 25, 2004
- "Brainwave Sensor Touted as Tool in Counter-Terrorism", Neurotech Reports (undated)
- OpenEEG — An open source hardware and software project to enable hobbyists to build their own EEG machine (mostly for biofeedback purposes).