Brain fingerprinting uses brain wave monitoring to determine if a subject has memories of specific facts relevant to a criminal case. It is different from a polygraph test and has been used in several high-profile cases in the US. The test measures brain waves when presented with visual or sound stimuli and can determine if a subject has a built-in memory of a specific stimulus. The technology has been declared admissible in court, but limitations arise when the subject becomes aware of evidence during the investigation. Critics point to some inaccurate results, but proponents argue that the MERMER method is more accurate than the original P300 method.
Brain fingerprinting is a recently developed forensic technique that uses brain wave monitoring to determine whether a subject of a criminal investigation has memories of specific facts relevant to the case embedded in his or her brain. The technology has been used in several high-profile cases in the United States and has been declared admissible in court. Dr. Lawrence Farwell created the technology in the early 1990s, basing it on a brain wave known as P300 that is emitted when a subject recognizes a stimulus placed in front of him or her. This process is somewhat limited in criminal investigations if the subject has already heard of the facts in the case and critics have condemned the process as not entirely accurate.
The brain fingerprinting test is administered by computer and is different from a polygraph, or lie detector test, in that it does not seek any verbal responses from its subjects. Measures the subject’s brain waves when presented with visual or sound stimuli. Some of the stimuli are called “targets” and are previously known to the subject, thus providing a baseline brain wave for the test. Other stimuli irrelevant to the case are presented, but a third group of stimuli, called “probes,” are elements of the case or crime scene that have not previously been presented to the subject by the investigators.
When the subject sees or hears these probes, their brain waves are measured by electronic sensors mounted on a headband worn during the test. It is possible that the probe produces a brain response that Dr. Farwell has classified as a multifaceted memory-related and coded electroencephalographic response, or MERMER, which includes a traditional P300 response along with other measurable brain patterns that provide further evidence that the subject recognizes the stimulus. If so, it is determined that the subject has a built-in memory of the specific stimulus, also called the “present memory” response. No MERMER response means it has not recognized the probe, a “no memory” response.
US courts have used brain fingerprinting in several prominent cases and have ruled that the procedure is legally admissible as evidence. In 1999, serial killer JB Grinder pleaded guilty to a crime of rape and murder committed 15 years earlier after brain fingerprints showed he had memory of specific details of the crime. The use of technology helped clear an Iowa man named Terry Harrington in 2003 of a crime he committed 26 years earlier, as her brainwave responses confirmed his alibi.
Trial limitations arise when the subject of an investigation becomes aware of evidence and other elements of the case during the investigation or even after learning about it from the media. Also, brain prints can usually only prove whether a subject was at the crime scene, not whether they committed the crime. Critics of brain fingerprinting point to some inaccurate results from the P300 studies, although proponents argue that Dr. Farwell’s MERMER method is a vast improvement over the original P300 method in terms of accuracy.
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