Advocates of brain fingerprinting have struggled to prove its value, and since 9/11 it has had some renewed popularity among researchers, politicians and the media as a potential anti-terrorist screening measure. A suspected terrorist could be shown captured terrorist documents, photos of other terrorists, and other materials in order to gauge recognition. With so much at stake for the suspect, one would hope that the machine's accuracy is as high as its proponents claim.
The device works by monitoring certain brainwaves while images, sounds, and/or phrases are presented to the subject... familiar items will trigger certain brain pathways, while unfamiliar items will trigger others. A headband connected to an Electroencephalography (EEG) machine scans for the brainwaves in question, and in theory, this method will determine whether a suspect had prior knowledge of the event or activity. The method is called "brain fingerprinting," and it aims to be what the lie detector never was... an infallible witness.
Similar to polygraph testing, the machine's operator must establish a reference to use as a baseline for the test. When the test begins, the subject is exposed to a series of familiar and unfamiliar stimuli, and the results are recorded. This will calibrate the machine to the subject's "familiar" and "unfamiliar" brainwave patterns. The subject is then provided with the relevant stimuli, and the machine measures the familiarity response. There is no need for verbal interaction with the subject since the brain's activity is directly monitored.
Currently, a large portion of the scientific community has strong doubts regarding the reliability of brain fingerprinting, believing it to be no more dependable than a classic polygraph test. Several experiments have demonstrated that a disciplined person can be trained to control the EEG response of his or her brain by imagining emotional events as the stimuli are presented, which would potentially allow them to defeat the test. It also appears that the studies which indicated 99.9% accuracy with no false positives were entirely based on hand-selected participants and limited questioning, not on real-world scenarios with unknown suspects.
Some still believe the test to be almost 100% accurate, which is a dangerous notion. No machine is infallible, particularly considering the machines' imperfect operators: humans. A human operator could deliberately or accidentally alter the results of a test to bring about positive or negative results. Consider too that it was humans who chose to call the technique "brain fingerprinting," despite the fact that most brains do not have fingers. Even if the machine proves useful in criminal investigations, there needs to be a reasonable margin for error given the human factor.
In a test almost two years ago, convicted murderer Jimmy Ray Slaughter was subjected to brain fingerprinting (pictured, top), and the test indicated that he was unfamiliar with the crime scene. But brain fingerprinting evidence is not admissible in most courts, and Jimmy Ray was executed by the state of Oklahoma in March of 2005. In another case, the state of Iowa did allow brain fingerprinting evidence to be admitted, and won a retrial for convicted killer Terry Harrington.
Scientists keep hunting for foolproof ways to detect human lies, and some new technologies using fMRI and PET scans are being researched. One day, perhaps, the information will be directly read from the brain like data from a hard drive, and the guilty will be condemned by their own memories. Ah, technology.