Brain fingerprinting is a controversial technique that is advocated as a way to identify a terrorist or other dangerous person by measuring the "brainprint" of that person when shown a particular body of writing or an image that was previously familiar (such as of a training camp or manual). The brainprint is based on the P300 complex, a series of well-known brainwave components that can be measured. The technique is said to be more effective than a lie detector test.
The inventor of the technique, Dr. Lawrence Farwell, has used the technique in at least one court case to determine the innocence of a man convicted of murder and the guilt of his accuser. Farwell showed each person pictures of the crime scene and measured their brainwave responses to determine which person had seen the crime scene before. Claiming that the test is 99.99% infallible, Falwell's test convinced the court to free the convicted person. The real perpetrator pleaded guilty.
In the test, the subject is fitted with a patented headband equipped with sensors and shown a series of relevant words or pictures on a computer screen. When the brain recognizes something familiar, the brain elicits a wavelike response known as a MERMER (memory and encoding-related multifaceted electroencephalographic response). The MERMER in turn contains the brain response known as a P300. The test can be done in as little as 10 minutes.
As a counter-terrorist measure at airports or other places, the technique, if mandated, could be challenged as a possible invasion of privacy. Critics also question whether brain fingerprinting could be administered efficiently and without a considerable number of false readings. They also ask how it could be used to screen for terrorists who had not been exposed to the words or pictures being shown.