Brain fingerprinting

Brain fingerprinting (BF) is a lie detection technique which uses brain waves from a electroencephalography (EEG) to determine whether specific information is stored in the subject's cognitive memory. It was invented by Larry Farwell, a Harvard-graduated neuroscientist, and published in 1995. The technique involves presenting words, phrases, or pictures containing salient details about a crime on a computer screen, in a series with other, irrelevant stimuli to identify whether the suspect recognizes the crime-related items. Although brain fingerprinting has been used in investigations, the test results themselves can not be admitted as evidence in a legal trial.

The assumption underpinning the application of BF is that the culprit has concealed information about the crime stored in the brain and it can be revealed by analysing fluctuations in the brainwaves that measure a human's neurological activity. Brain fingerprinting relies on two major components, specificity and recognition, as it is assumed that the culprit of the crime will recognize certain details of the investigation whilst innocent subjects will not, based on the familiarity of the items presented. For example, only a guilty individual will have concealed information about the specific gun used in a crime.

P300 response
The procedure begins by attaching sensors called electrodes to the subject's scalp to form a circuit that quantifies brain activity using a test called an electroencephalogram (EEG). When conducting an EEG to measure electrical activity in the brain, a distinctive surge of electrical activity may appear between 300 and 800 milliseconds – this is referred to as the P300 response, first introduced in the 1960s. This psychophysiological response signals one's reaction to seeing a familiar object immediately after being exposed to the stimulus. Based on this information, scientists have argued that they can accurately convict a guilty suspect. Although the origins of this neurological response are unclear, the phenomenon has been extensively studied and peer-reviewed for over 100 years.

Contrary to a traditional polygraph (also known as a lie detector) that relies on changes to sweat glands as nervous responses to determine the subject's honesty, brain fingerprinting is entirely concealed in the brain's responses to stimuli. This makes the technique harder to resist or beat, making it a more reliable method of detecting lies. The P300 response is supported by at least 80 laboratory experiments that use the Guilty Knowledge Test (GKT). The GKT, also known as the Concealed Information Test (CIT), is an alternative method of interrogation to reveal concealed information a culprit might have about a crime. Similarly, it focuses on measuring the physiological reaction of subjects, although it prioritises electrodermal, respiratory and cardiovascular responses rather than neurological activity.

History
Brain fingerprinting was first used in a criminal case in 1999, when a man named James Grinder confessed to committing a murder that happened 15 years prior. In a short time after his confession, he retracted his statements. The police struggled to incriminate Grinder because the evidence was outdated. The police and FBI reached out to Lawrence Farwell with the aim of using BF to obtain enough evidence to incriminate Grinder. Soon after taking the test, Grinder confessed to the murder of Julie Helton and three other people, securing him life imprisonment. This case was not the last time Farwell worked in collaboration with a US Intelligence Community as the CIA went on to fund Farwell's counterterrorism research for the US Navy, which was published by Frontiers in Neuroscience.

In 2001, the US Federal Agency outlined how brain fingerprinting was only to be used as an investigative tool; however, several intelligence agencies came forth saying that despite the support and funds they had provided to the development of this technology, they were not to use it at all because of its lack of applicability. Following the US court's rejection of BF, Farwell redirected his resources to advertising the technology abroad. He has worked alongside several government agencies, such as in the United Arab Emirates, and justice systems in India and New Zealand. Nevertheless, his technology has not yet achieved a widespread presence in any criminal setting around the world, and results of brainwave analysis are often not admissible as evidence in court.

Criticism
Following extensive and ongoing research on the brain fingerprinting protocol for detecting deception and its decisive contribution to several trials, the accuracy of technology has been the subject of speculation for a decade. J Peter Rosenfeld found methodological problems associated with brain fingerprinting and related methods. Other researchers have argued that Farwell is misleading and misrepresenting the scientific status of brain fingerprinting technology. Additional studies have attempted to determine the success rate of BF, given that Farwell has claimed a 100% success rate for the technology and a lack of both false positives and negatives in his research. When carrying out comparative studies between the common polygraph lie detector and brain fingerprinting, the latter appears to have fewer false positives; however, when questioned about specific details, the P300 technique seems to be less reliable.

The legitimacy of brain fingerprinting is still questioned. The lack of replication of his studies is largely due to legal restrictions regarding the use of his software and apparatus appointed by the patent issued to Farwell in 1994. This controversy is enhanced by discussion surrounding the patent rights and the fraudulent behaviour of the developer Larry Farwell regarding fabricated FBI reports. Brainwave Sciences, the technology company that owns BF, tainted the validity of the technique when some of its board members became the focal spotlights of scandals in the US. As a result, the acceptance of BF is still the subject of controversy and debate among scholars and legal institutions.

Current research
A research team in New Zealand conducted an examination of Farwell's technology and found that current forensic brainwave analysis (FBA) methods did not meet standards for foundational validity (validity in lab settings) set in the Report to the President on Forensic Science in Criminal Courts: Ensuring Scientific Validity of Feature-Comparison Methods. However, they argued that the technique has the potential to serve as a useful tool in civil and criminal justice if its validity can be conclusively established. Two pilot studies exploring FBA have been conducted, and preliminary results suggest the need for further research to determine the accuracy, validity and reliability of FBA.

A recent review by Rosenfeld found that the P300 response has proven resistant and accurate.

Brain fingerprinting has made appearances in the media. In 2018, Larry Farwell's technique made a brief appearance in the second season of Netflix's Making a Murderer; however, his findings were not considered during the trial as he was using unauthorized software.

Since 2020, the application of brain fingerprinting has changed. Most recently, the term "brain fingerprinting" referred to the uniqueness of brains from a functional neuroimaging context. This new field of study aims to predict patterns of brain connectivity to hopefully prognosticate mental disorders in the future.