Brain fingerprinting

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Brain fingerprinting is a controversial forensic science technique that uses electroencephalography (EEG) to determine whether specific information is stored in a subject's brain. It does this by measuring electrical brainwave responses to words, phrases, or pictures that are presented on a computer screen (Farwell & Smith 2001, Farwell, Richardson, and Richardson 2012).


Brain fingerprinting was invented by Lawrence Farwell. The theory is that the brain processes known and relevant information differently from the way it processes unknown or irrelevant information (Farwell & Donchin 1991). The brain's processing of known information, such as the details of a crime stored in the brain, is revealed by a specific pattern in the EEG (electroencephalograph) (Farwell & Smith 2001, Farwell 1994). Farwell's brain fingerprinting originally used the well-known P300 brain response to detect the brain's recognition of the known information (Farwell & Donchin 1986, 1991; Farwell 1995a). Later Farwell discovered the P300-MERMER ("Memory and Encoding Related Multifaceted Electroencephalographic Response"), which includes the P300 and additional features and is reported to provide a higher level of accuracy and statistical confidence than the P300 alone (Farwell & Smith 2001, Farwell 1994, Farwell 1995b, Farwell et al. 2012). Farwell and colleagues report less than 1% error rate in laboratory research (Farwell & Donchin 1991) and real-life field applications (Farwell & Smith 2001, Farwell et al. 2012). In independent research William Iacono and others who followed identical or similar scientific protocols to Farwell's have reported a similar low level of error rate and high statistical confidence (e.g., Allen & Iacono 1997). Farwell's standards for brain fingerprinting tests are specified in Farwell 2012 and Farwell et al. 2012).

Brain fingerprinting has been ruled admissible in court (Harrington v. State 2001, Farwell & Makeig 2005, Farwell 2012), and applied in a number of high-profile criminal cases, including the exoneration of Terry Harrington after he had been convicted of murder (Harrington v. State 2001).

Brain fingerprinting technique has been criticized on a number of fronts (Fox 2006b, Abdollah 2003). Although independent scientists who have used the same or similar methods as Farwell's brain fingerprinting have achieved similar, highly accurate results (Allen & Iacono 1997; see also Harrington v. State 2001, Farwell 2012), different methods have yielded different results. J. Peter Rosenfeld used P300-based tests incorporating fundamentally different methods, resulting in as low as chance accuracy (Rosenfeld et al. 2004) as well as susceptibility to countermeasures, and criticized brain fingerprinting based on the premise that the shortcomings of his alternative technique should generalize to all other techniques in which the P300 is among the brain responses measured, including brain fingerprinting.


The technique uses the well-known fact that an electrical signal known as P300 is emitted from an individual's brain beginning approximately 300 milliseconds after it is confronted with a stimulus of special significance, e.g. a rare vs. a common stimulus or a stimulus the subject is asked to count (see P300, Gaillard and Ritter 1983, and Picton 1988 for a comprehensive discussion of this effect). The application of this in brain fingerprinting is to detect the P300 as a response to stimuli related to the crime or other investigated situation, e.g., a murder weapon, victim's face, or knowledge of the internal workings of a terrorist cell (Farwell 1992a, Farwell & Donchin 1991, Harrington v. State 2001, Farwell 2012, Farwell et al. 2012). Because it is based on EEG signals, the system does not require the subject to issue verbal responses to questions or stimuli.

The person to be tested wears a special headband with electronic sensors that measure the EEG from several locations on the scalp. The subject views stimuli consisting of words, phrases, or pictures presented on a computer screen. Stimuli are of three types: 1) "irrelevant" stimuli that are irrelevant to the investigated situation and to the test subject, 2) "target" stimuli that are relevant to the investigated situation and are known to the subject, and 3) "probe" stimuli that are relevant to the investigated situation and that the subject denies knowing. Probes contain information that is known only to the perpetrator and investigators, and not to the general public or to an innocent suspect who was not at the scene of the crime. Before the test, the scientist identifies the targets to the subject, and makes sure that he/she knows these relevant stimuli. The scientist also makes sure that the subject does not know the probes for any reason unrelated to the crime, and that the subject denies knowing the probes. The subject is told why the probes are significant (e.g., "You will see several items, one of which is the murder weapon"), but is not told which items are the probes and which are irrelevant (Farwell 1994, Farwell 2012, Farwell et al. 2012).

Since brain fingerprinting uses cognitive brain responses, brain fingerprinting does not depend on the emotions of the subject, nor is it affected by emotional responses (Farwell & Smith 2001, Farwell 1992a, 1995a, Farwell 2012). Brain fingerprinting is fundamentally different from the polygraph (lie-detector), which measures emotion-based physiological signals such as heart rate, sweating, and blood pressure (Farwell 1994). Also, unlike polygraph testing, it does not attempt to determine whether or not the subject is lying or telling the truth. Rather, it measures the subject's brain response to relevant words, phrases, or pictures to detect whether or not the relevant information is stored in the subject's brain (Farwell & Smith 2001, Harrington v. State 2001, Farwell 2012).

By comparing the responses to the different types of stimuli, the brain fingerprinting system mathematically computes a determination of "information present" (the subject knows the crime-relevant information contained in the probe stimuli) or "information absent" (the subject does not know the information) and a statistical confidence for the determination. This determination is mathematically computed, and does not involve the subjective judgment of the scientist (Farwell et al. 2012).

Background and terminology[edit]

"Brain fingerprinting" is a computer-based test that is designed to discover, document, and provide evidence of guilty knowledge regarding crimes, and to identify individuals with a specific training or expertise such as members of dormant terrorist cells or bomb makers. It has also been used to evaluate brain functioning as a means of early detection of Alzheimer's and other cognitively degenerative diseases, and to evaluate the effectiveness of advertising by measuring brain responses.

The technique is described in Dr. Farwell's paper "Using Brain MERMER Testing to Detect Concealed Knowledge Despite Efforts to Conceal", published in the Journal of Forensic Sciences in 2001 by Dr. Farwell and FBI Supervisory Special Agent Sharon Smith of the FBI (Farwell & Smith 2001), and in other peer-reviewed publications. For a review, see Farwell 2012; see also Farwell et al. 2012.

These papers describe tests 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 is significant in context (for example, in the context of a crime) (Gaillard & Ritter 1983, Farwell & Donchin 1991). When an irrelevant stimulus is presented, a P300 is not expected to occur (Picton 1988, Farwell & Donchin 1991, Farwell & Smith 2001). The P300 is widely known in the scientific community, and is also known as an oddball-evoked P300 (see Harrington v. State 2001 and P300).

While researching the P300, Dr. Farwell created a more detailed test that not only includes the P300, but also observes the stimulus response up to 1400 milliseconds after the stimulus. He calls this brain response a P300-MERMER, memory and encoding related multifaceted electroencephalographic response. The P300, an electrically positive component, is maximal at the midline parietal area of the head and has a peak latency of approximately 300 to 800 milliseconds. The P300-MERMER includes the P300 and also includes an electrically negative component, with an onset latency of approximately 800-1200ms (Farwell 1994, Farwell & Smith 2001, Farwell 2012, Farwell et al. 2012). According to Dr. Farwell, the P300-MERMER includes additional features involving changes in the frequency of the EEG signal, but for the purposes of signal detection and practical application the P300-MERMER is sufficiently characterized by the P300 and the following negative component in the brain response (Farwell 1994, Farwell 2012, Farwell et al. 2012).

Current uses and research[edit]

Brain Fingerprinting has two primary applications: 1) detecting the record of a specific crime, terrorist act, or incident stored in the brain (Farwell & Smith 2001, Farwell et al. 2012), and 2) detecting a specific type of knowledge, expertise, or training, such as knowledge specific to FBI agents, Al-Qaeda -trained terrorists, or bomb makers (Farwell 1992b, Farwell 1993, Farwell et al. 2012). For a review, see Farwell 2012.

The seminal paper by Dr. Farwell and Emmanuel Donchin (Farwell & Donchin 1991) reported successful application of the technique in detecting knowledge of both laboratory mock crimes and real-life events, with no false positives and no false negatives.

In a study with the FBI, Dr. Farwell and FBI scientist Drew Richardson, former chief of the FBI's chem-bio-nuclear counterterrorism unit, used brain fingerprinting to show that test subjects from specific groups could be identified by detecting specific knowledge which would only be known to members of those groups (Farwell et al. 2012). A group of 17 FBI agents and 4 non-agents were exposed to stimuli (words, phrases, and acronyms) that were flashed on a computer screen. The probe (situation-relevant) stimuli contained information that would be common knowledge only to someone with FBI training. Brain fingerprinting correctly distinguished the FBI agents from the non-agents.

The CIA has also funded Farwell's research (Dale 2001). In a study funded by the CIA, Farwell and colleagues (Farwell et al. 2006) used brain fingerprinting to detect which individuals had US Navy military medical training. All 30 subjects were correctly determined to have or not to have the specific information regarding military medicine stored in their brains. In another CIA-funded study, brain fingerprinting correctly detected which individuals had participated in specific real-life events, some of which were crimes, based on the record stored in their brains. Error rate was again 0%; accuracy was 100% (Farwell et al. 2012). Dr. Farwell collaborated with FBI scientist Sharon Smith in a further study in which brain fingerprinting detected real-life events that was published in the Journal of Forensic Sciences (Farwell & Smith 2001).

Dr. Farwell's recent studies, many conducted with former FBI scientist Dr. Drew Richardson, have mostly involved detecting real-life information in field conditions. Farwell and Richardson applied brain fingerprinting in detecting information regarding actual crimes with real-world judicial consequences, including multiple murders (Farwell et al. 2012). In one study they tested brain fingerprinting in detecting information unique to bomb makers (experts in improvised explosive devices, IEDs), for application in national security and counterterrorism. Error rate was 0%; that is, 100% of subjects in these studies were correctly detected (Farwell et al. 2012). Dr. Farwell has also offered a $100,000 reward for beating a brain fingerprinting field test(KOMO News 2008). To date, no one has ever succeeded in doing so (Farwell et al. 2012).

Use in criminal investigation[edit]

Dr. Lawrence Farwell conducts a Brain Fingerprinting test on Terry Harrington.
Dr. Lawrence Farwell conducts a Brain Fingerprinting test on serial killer JB Grinder.

Farwell's brain fingerprinting has been ruled admissible in court in the reversal of the murder conviction of Terry Harrington (Harrington v. State 2001, Farwell & Makeig 2005). Following a hearing on post-conviction relief on November 14, 2000, an Iowa District Court stated that the fundamental science involved in Dr. Farwell's brain fingerprinting P300 test was well established in the scientific community. For a range of reasons, however, the court dismissed the defendant's petition for a new trial.

In order to be ruled admissible under the prevailing Daubert standard established by the US Supreme Court, the District Court required proof that brain fingerprinting 1) has been tested and proven, 2) has been peer reviewed and published, 3) produces a known (and low) error rate and is systematically applied, and 4) is well accepted in the relevant scientific community. In ruling the brain fingerprinting test admissible as scientific evidence, the Court stated the following:

"In the spring of 2000, Harrington was given a test by Dr. Lawrence Farwell. The test is based on a 'P300 effect'."

"The P-300 effect has been recognized for nearly twenty years."

"The P-300 effect has been subject to testing and peer review in the scientific community."

"The consensus in the community of psycho-physiologists is that the P300 effect is valid."

"The evidence resulting from Harrington's ‘brain fingerprinting’ test was discovered after the fact. It is newly discovered."

(Harrington v. State 2001)

As the Iowa District Court clearly stated, the results of the brain fingerprinting test on Harrington constituted "evidence" that the court admitted. Dr. Farwell's testimony as an expert witness and the testimony of the other two expert witnesses in the case also were admitted as evidence. The Iowa court admitted the brain fingerprinting evidence and Dr. Farwell's testimony on it under the Daubert standard.

Several authors of law articles have examined the admissibility of brain fingerprinting evidence in the Harrington case in depth and detail, and summarized the outcome as follows.

"The Judge in Harrington ruled Brain Fingerprinting admissible under Daubert after conducting a day-long hearing featuring three expert witnesses, each renowned in his field." (Roberts in Yale Journal of Law and Technology 2007, p. 265)

"In Harrington, the court admitted Dr. Farwell's testimony on brain fingerprinting and stated that it satisfied the Daubert test." (Moenssens in University of Missouri-Kansas City Law Review, p. 26)

"[T]he [Harrington] court admitted Brain Fingerprinting evidence based upon the P300 effect…" (Erickson in Drake Law Review, p. 13)

The court noted the distinction, however, between admissibility and weight. In light of the circumstances of a particular case, admissible evidence does not always have sufficient weight to produce a verdict in favor of the side which proffers the evidence. Although the court ruled brain fingerprinting admissible, the court ruled that the weight of the brain fingerprinting evidence and other evidence proffered by Harrington would probably not have been sufficient to change the verdict in the original trial.

"The court determined that Brain Fingerprinting was new evidence not available at the original trial, and that it was sufficiently reliable to merit admission of the evidence; however, the court did not regard its weight as sufficiently compelling in light of the record as a whole as meeting its exacting standard, and thus it denied a new trial on this and the other grounds asserted by Harrington."(Farwell and Makeig in Open Court, p. 9)

The court ruled in Harrington's favor on two major issues, but nevertheless denied him a new trial. The court ruled brain fingerprinting and the testimony of the expert witnesses on it were admissible, and also admitted the recantation testimony of the only alleged witness to the crime, yet nevertheless denied Harrington's petition for a new trial. Regarding this rather complicated ruling, one commentator opined that "[t]he Harrington court avoided a clear ruling on admissibility" (Denno 2002) of the test.

Harrington appealed to the Iowa Supreme Court. The Iowa Supreme Court reversed the trial court and granted Harrington a new trial. (Harrington v. State 2003, p. 516) The supreme court did not reach the brain fingerprinting issue, and decided the case on other grounds. "Because the scientific testing evidence is not necessary to a resolution of this appeal, we give it no further consideration." (Harrington v. State 2003, p. 516)

Although the Iowa Supreme Court did not rule on brain fingerprinting, they allowed the law of the case established by the district court to stand, implicitly including the district court's finding regarding the "newly discovered" "evidence" "resulting from Harrington's Brain Fingerprinting test." (Harrington v. State 2003)

Due to a constitutional rights violation, specifically a Brady violation, by the State of Iowa in the original trial, the Iowa Supreme Court awarded Harrington a new trial. The only alleged witness to the crime, Kevin Hughes, recanted when Dr. Farwell confronted him with the "information absent" results of the brain fingerprinting test on Harrington. Without its star witness, the state subsequently dismissed the murder prosecution without prejudice for lack of evidence due to witness recantations and the passage of time.

The State of Iowa had argued unsuccessfully in trial court that the brain fingerprinting results should not be considered admissible "evidence," whether "newly discovered" or not (Harrington v. State 2001). After the Supreme Court reversed Harrington's conviction and granted him a new trial, the Iowa Attorney General's Office issued a press release restating this position, and also restating the fact that the Iowa Supreme Court did not rule on brain fingerprinting.

"With one Justice dissenting, the Supreme Court reversed Harrington's conviction on the ground that the failure to disclose police reports denied defendant a fair trial. The Court ruled that withholding the reports compromised Harrington's defense at trial that he was not the person who shot Mr. Schweer."

"The Court also declined to rule on the admissibility or credibility of the "brain fingerprinting" evidence offered by Harrington. In its brief and argument to the Court, the State argued that brain fingerprinting is "junk science" that has no track record establishing its reliability. The State argued that the technique has been tested in the lab with fewer than 200 persons and has been used in the field in only a handful of cases. The State argued the technique should be treated similarly to lie-detector tests, which are inadmissible in Iowa and most other states. The Iowa Supreme Court did not determine the reliability of brain fingerprinting and did not rule on the admissibility of brain fingerprinting in Iowa courts." (Press release by Iowa Attorney General's Office)

In his recantation, Hughes stated under oath under questioning by Farwell that the detectives and prosecutors had told him he would go to prison for life if he didn’t implicate Harrington. He stated that when he agreed to falsely accuse Harrington of the murder, they coached him in fabricating the story to which he later testified in the trial. He stated that when he said something that contradicted known facts – such as identifying the wrong murder weapon – they corrected him, and he changed his story accordingly. (Harrington v. State 2001)

Harrington sued the prosecutors and the State of Iowa for framing him. The prosecutors and the State of Iowa did not deny the accusations brought by Hughes and Harrington. Their defense was that they enjoyed absolute immunity due to their professional positions. The US Supreme Court agreed to hear the case on the issue, as ‘’TIME magazine’’ put it, of "When Is It Legal to Frame a Man for Murder?" (TIME Magazine article on Harrington) (TIME 2009). Before the Supreme Court heard the case, however, the State of Iowa settled with Harrington and another man falsely convicted of the same crime. The state paid them a $12 million settlement (L A Times 2010).

Brain Fingerprinting testing was also instrumental in bringing serial killer James B. Grinder to justice. In August 1999 Dr. Farwell conducted a brain fingerprinting test on Grinder at the request of Sheriff Robert Dawson of Macon County, Missouri. The test proved that information stored in his brain matched the details of the murder of Julie Helton (Farwell et al. 2012, Farwell 2012). Faced with a certain conviction and almost certain death sentence, Grinder then pled guilty to the rape and murder of Julie Helton in exchange for a sentence of life in prison without parole. He is currently serving that sentence, and has also confessed to the murders of three other women.

Limitations of brain fingerprinting[edit]

Both the strengths and limitations of brain fingerprinting are documented in detail in the expert witness testimony of Dr. Farwell and two other expert witnesses in the Harrington case (Harrington v. State 2001) as well as in Farwell's publications and patents (e.g., Farwell 1994, Farwell 1995a, b, Farwell & Smith 2001, Farwell 2012). The limitations of brain fingerprinting described below are also summarized in PBS 2004, PBS Innovation Series – "Brain Fingerprinting: Ask the Experts".

Brain fingerprinting detects information-processing brain responses that reveal what information is stored in the subject's brain. It does not detect how that information got there. This fact has implications for how and when the technique can be applied. In a case where a suspect claims not to have been at the crime scene and has no legitimate reason for knowing the details of the crime, and investigators have information that has not been released to the public, brain fingerprinting can determine objectively whether or not the subject possesses that information. In such a case, brain fingerprinting could provide useful evidence.

If, however, the suspect knows everything that the investigators know about the crime for some legitimate reason, then the test cannot be applied. There are several circumstances in which this may be the case. If a suspect acknowledges being at the scene of the crime, but claims to be a witness and not a perpetrator, then the fact that he knows details about the crime would not be incriminating. There would be no reason to conduct a test, because the resulting "information present" response would simply show that the suspect knew the details about the crime – knowledge which he already admits and which he gained at the crime scene whether he was a witness or a perpetrator.

Another case where brain fingerprinting is not applicable would be one wherein a suspect and an alleged victim – say, of an alleged sexual assault – agree on the details of what was said and done, but disagree on the intent of the parties. Brain fingerprinting detects only information, and not intent. The fact that the suspect knows the uncontested facts of the circumstance does not tell us which party's version of the intent is correct.

In a case where the suspect knows everything that the investigators know because he has been exposed to all available information in a previous trial, there is no available information with which to construct probe stimuli, so a test cannot be conducted. Even in a case where the suspect knows many of the details about the crime, however, it is sometimes possible to discover salient information that the perpetrator must have encountered in the course of committing the crime, but the suspect claims not to know and would not know if he were innocent. This was the case with Terry Harrington (Harrington v. State 2001). By examining reports, interviewing witnesses, and visiting the crime scene and surrounding areas, Dr. Farwell was able to discover salient features of the crime that Harrington had never been exposed to at his previous trials. The brain fingerprinting test showed that the record in Harrington's brain did not contain these salient features of the crime, but only the details about the crime that he had learned after the fact.

Obviously, in structuring a brain fingerprinting test, a scientist must avoid including information that has been made public. Detecting that a suspect knows information he obtained by reading a newspaper would not be of use in a criminal investigation, and standard brain fingerprinting procedures eliminate all such information from the structuring of a test (Farwell 1995a, Harrington v. State 2001, Farwell 2012). News accounts containing many of the details of a crime do not interfere with the development of a brain fingerprinting test, however; they simply limit the material that can be tested. Even in highly publicized cases, there are almost always many details that are known to the investigators but not released to the public (Farwell 2012), and these can be used as stimuli to test the subject for knowledge that he would have no way to know except by committing the crime.

Another situation where brain fingerprinting is not applicable is one where the authorities have no information about what crime may have taken place. For example, an individual may disappear under circumstances where a specific suspect had a strong motive to murder the individual. Without any evidence, authorities do not know whether a murder took place, or the individual decided to take a trip and tell no one, or some other criminal or non-criminal event happened. If there is no known information on which a suspect could be tested, a brain fingerprinting test cannot be structured.

Similarly, brain fingerprinting is not applicable for general screening, for example, in general pre-employment or employee screening wherein any number of undesirable activities or intentions may be relevant. If the investigators have no idea what crime or undesirable act the individual may have committed, there is no way to structure appropriate stimuli to detect the telltale knowledge that would result from committing the crime. Brain fingerprinting can, however, be used for specific screening or focused screening, when investigators have some idea what they are looking for. For example, brain fingerprinting can be used to detect whether a person has knowledge that would identify him as an FBI agent, an Al-Qaeda-trained terrorist, a member of a criminal organization or terrorist cell, or a bomb maker (Farwell et al. 2006).

Brain fingerprinting does not detect lies. It simply detects information. No questions are asked or answered during a brain fingerprinting test. The subject neither lies nor tells the truth during a brain fingerprinting test, and the outcome of the test is unaffected by whether he has lied or told the truth at any other time. The outcome of "information present" or "information absent" depends on whether the relevant information is stored in the brain, and not on what the subject says about it (Farwell 1994, PBS 2004, Farwell 2012).

Brain fingerprinting does not determine whether a suspect is guilty or innocent of a crime. This is a legal determination to be made by a judge and jury, not a scientific determination to be made by a computer or a scientist (Farwell 1994, PBS 2004, Farwell 2012). Brain fingerprinting can provide scientific evidence that the judge and jury can weigh along with the other evidence in reaching their decisions regarding the crime. To remain within the realm of scientific testimony, however, a brain fingerprinting expert witness must testify only regarding the scientific test and information stored in the brain revealed by the test, as Dr. Farwell did in the Harrington case (Harrington v. State 2001). Like the testimony of other forensic scientists, a brain fingerprinting scientist's testimony does not include interpreting the scientific evidence in terms of guilt or innocence. A DNA expert may testify that two DNA samples match, one from the crime scene and one from the suspect, but he does not conclude "this man is a murderer." Similarly, a brain fingerprinting expert can testify to the outcome of the test that the subject has specific information stored in his brain about the crime (or not), but the interpretation of this evidence in terms of guilt or innocence is solely up to the judge and jury (Harrington v. State 2001, PBS 2004).

Just as all witness testimony depends on the memory of the witness, brain fingerprinting depends on the memory of the subject. Like all witness testimony, brain fingerprinting results must be viewed in light of the limitations on human memory and the factors affecting it (Harrington v. State 2001, PBS 2004). Brain fingerprinting can provide scientific evidence regarding what information is stored in a subject's brain. It does not determine what information should be, could be, or would be stored in the subject's brain if the subject were innocent or guilty. It only measures what actually is stored in the brain (Farwell 2012). How this evidence is interpreted, and what conclusions are drawn based on it, is outside the realm of the science and the scientist. This is up to the judge and jury. It is up to the prosecutor and the defense attorney to argue, and the judge and jury to decide, the significance and weight of the brain fingerprinting evidence in making a determination of whether or not the subject committed the crime.

Like all forensic science techniques, brain fingerprinting depends on the evidence-gathering process which lies outside the realm of science to provide the evidence to be scientifically tested. Before a brain fingerprinting test can be conducted, an investigator must discover relevant information about the crime or investigated situation. This investigative process, in which the investigator gathers the information to be tested from the crime scene or other sources related to the crime, depends on the skill and judgment of the investigator. This process is outside the scientific process; it precedes the scientific process of brain fingerprinting. This investigative process produces the probe stimuli to be tested. Brain fingerprinting science only determines whether the information tested is stored in the brain of the subject or not. It does not provide scientific data on the effectiveness of the investigation that produced the information about the crime that was tested. In this regard, brain fingerprinting is similar to other forensic sciences. A DNA test determines only whether two DNA samples match, it does not determine whether the investigator did an effective job of collecting DNA from the crime scene. Similarly, a brain fingerprinting test determines only whether or not the information stored in the suspect's brain matches the information contained in the probe stimuli. This is information that the investigator provided to the scientist to test scientifically, based on the investigative process that is outside the realm of science. In making their determination about the crime and the suspect's possible role in it, the judge and jury must take into account not only the scientific determination of "information present" or "information absent" provided by the brain fingerprinting test; they must also make common-sense, human, non-scientific judgments regarding the information gathered by the investigator and to what degree knowledge or lack of knowledge of that information sheds light on the suspect's possible role in the crime (Harrington v. State 2001, Farwell1995a, Farwell 2012). Brain fingerprinting is not a substitute for effective investigation on the part of the investigator or for common sense and good judgment on the part of the judge and jury (PBS 2004).

A report by the United States General Accounting Office (now called Government Accountability Office) in 2001 reported that the scientists it interviewed (including Farwell, Iacono, Richardson, Rosenfeld, Smith, Donchin, and others) all had expressed a need for more research to investigate brain fingerprinting's application as forensic science tool. (Initial Pre-911 GAO Report While they were unanimous in their support of more scientific research, scientists and others expressed widely varying views on the social policy question of whether brain fingerprinting should continue to be applied to bring criminals and terrorists to justice and to free innocent suspects while this research continues.

The initial GAO report was completed before the terrorist attacks of 9/11/2001. At that time, the primary interest of federal agencies in detection methods was for employee screening, rather than detecting terrorists. (As discussed above, brain fingerprinting is not applicable in general employee screening.) The initial, pre-911 GAO report stated that most of the individuals in various federal agencies interviewed at that time did not see brain fingerprinting playing a major role in their then-current operations. The report did not examine the science of brain fingerprinting; the published research at the FBI, the CIA, the US Navy, and elsewhere; the successful application of brain fingerprinting in criminal cases; or the success of brain fingerprinting in being ruled admissible in court. Since it was produced before the attacks of 9/11/2001, this initial report did not examine the application of brain fingerprinting in national security in the post-911 world. It did not discuss the application of brain fingerprinting in present-day criminal investigations and law enforcement.

Consequently, Senator Charles Grassley, who commissioned the initial report, has asked the GAO produce a new report that examines the value of brain fingerprinting in counterterrorism and criminal investigations in the post-911 world in light of published scientific research on the application of the technique in the laboratory and the field (Fox 2006a).

The initial GAO report was entitled "Federal Agency Views on the Potential Application of ‘Brain Fingerprinting.’" (Initial Pre-911 GAO Report). It was essentially a sampling of opinions of individuals associated with the polygraph in the federal government prior to 9-11. (It was completed before 9-11-2001 and issued shortly thereafter.) It reported that most such individuals did not see the need for brain fingerprinting in their pre-911 operations over a decade ago.

Individuals interviewed noted that their primary interest was general screening applications such as applicant screening and periodic employee screening, where the interrogator does not know what information he is seeking. Some individuals interviewed noted that they were satisfied with the performance of the polygraph for this purpose. Since brain fingerprinting detects information stored in the brain, not lies or deception, it is only applicable when the investigators have some idea what information they are looking for. For example, brain fingerprinting can detect the details of a specific crime stored in the brain, or the details of knowledge unique to FBI agents, or bomb makers, or Al-Qaeda-trained terrorists, or members of a particular terrorist cell. It is not applicable, however, in general screening situations, where the investigator has no idea what specific activities or crimes a person may have committed or what specific information is being sought. Before 9-11, the primary requirement for federal agencies was a general screening tool. The individuals interviewed by the GAO noted, correctly, that brain fingerprinting is not such a tool. Therefore, most of the individuals interviewed generally did not see brain fingerprinting as being useful for their primary purposes under the prevailing conditions prior to 9/11/2001.

Notable exceptions to this opinion were the only two FBI scientists who had actually conducted scientific research on brain fingerprinting and/or participated in its successful application in solving crimes, Dr. Drew Richardson and Dr. Sharon Smith. They both expressed the opinion that brain fingerprinting was highly valuable in FBI investigations.

Reflecting the views of most of those interviewed over a decade ago, before 9-11, the report stated:

"Officials representing CIA, DOD, Secret Service, and FBI do not foresee using the brain fingerprinting technique for their operations because of its limited application. For example, CIA and DOD officials indicated that their counterintelligence operations and criminal investigations do not usually lend themselves to a technique such as brain fingerprinting because use of the technique requires a unique level of detail and information that would be known only to the perpetrator and the investigators. These officials indicated that they need a tool to screen current and prospective employees, which as indicated above, involves questioning a subject about events unknown to the investigator. Further, a Secret Service official indicated that the agency has had a high success rate with the polygraph as an interrogative and screening tool and therefore saw limited use for brain fingerprinting."

The report noted, however, that the US government scientists interviewed who had conducted research on brain fingerprinting were convinced that it would be useful in FBI investigations.

The report did not include an account of the scientific research on brain fingerprinting or its successful use in court. The report did not discuss the value of brain fingerprinting for other applications other than general screening, for which it does not apply as discussed above. The GAO did not evaluate or opine on the effectiveness, accuracy, or validity of brain fingerprinting. The report stated:

"…we did not independently assess the hardware, software, or other components of the technology nor did we attempt to determine independently whether brain fingerprinting is a valid technique."

The report concluded that in general the federal officials involved with the polygraph who were interviewed did not see an immediate application for brain fingerprinting in their general screening operations before 9-11. Specific quotations to this effect follow.

Federal Agencies - "CIA, DOD, FBI, and Secret Service do not foresee using the Brain Fingerprinting technique for their operations because of its limited application."

DOD - "Overall, DOD officials indicated that Brain Fingerprinting has limited applicability to DOD's operations"

CIA - "From their experiences with the developer's research between 1991 and 1993, CIA officials concluded that Brain Fingerprinting had limited applicability to CIA's operations. Accordingly, CIA decided that it was not worth investing more funds to continue the developer's research." Secret Services - "The Service subsequently concluded that the technique had limited application to Secret Service activities."

Signed Letter from John E, Collingwood, Assistant Director, Office of Public and Congressional Affairs, to Mr Paul Jones, Director Justice Issues, Washington. The letter states (as quoted) - " In conclusion, the report fairly reflects the FBI's belief that this technique has limited applicability and usefulness to FBI investigative and personnel security matters. The FBI continues to support the view that this technique has limited utility. We also think it is important to point out that the rest of the federal community shares the FBI's view the Dr. Farwell's "Brain Fingerprinting" has very limited applicability and usefulness."

Signed Letter from Jack L Johnson, Jr, Special Agent in Charge, to Mr Paul Jones, Director Justice Issues, Washington. The letter states (as quoted) - " Dr Cantu has recently briefed me on this technology and the underlying scientific principals [sic], which purportedly support its accuracy and validity. Following this briefing, and a review of the information related to this technique, I must concur completely with the opinion of Dr Cantu. The "Brain Fingerprinting Technique" has very little applicability to the overall Secret Service mission, and is a technology that has not been completely validated as of this time."

The initial GAO report constituted a reasonably accurate opinion poll of federal employees involved with the polygraph over a decade ago, before 9/11, in a much different world. Note, however, that even at that time the FBI scientists who had relevant expertise and had actually conducted research on brain fingerprinting and used it successfully in field cases expressed the opinion that brain fingerprinting was valuable for FBI investigations. In any case, the opinions of non-expert federal employees over a decade ago are not relevant to the current applicability, validity, value, accuracy, or scientific merit of brain fingerprinting, or to its value in present-day national security and law enforcement operations.

Consequently Senator Grassley, who commissioned the original GAO report, has asked the GAO to develop a new report. He asked the GAO to discuss the potential applications of brain fingerprinting in criminal investigations and counterterrorism in the post-911 world. He also asked the GAO to include the views of experts well versed in brain fingerprinting and P300-MERMER technology, and to include the successful brain fingerprinting research at the FBI, CIA, and US Navy.

Future applications and research[edit]

After Dr. Farwell invented Brain Fingerprinting, he withheld it from the public for 15 years while he, his colleagues, and other, independent scientists tested it in the laboratory and in the field (Farwell 2012, ABC Good Morning America 2004). Farwell's decision to apply this science in real-life situations has been controversial (Dale 2001). In the years since Dr. Farwell first began applying the technology in the real world, proponents, including other scientists who have successfully applied the technique such as FBI scientist Drew Richardson, and those who have been freed or otherwise helped by brain fingerprinting, have advocated continuing and expanded application of the technology in the real world (ABC Good Morning America 2004, CBS 60 Minutes 2000). Critics, including some scientists, and those whose criminal activities have been thwarted by brain fingerprinting have advocated further delay in applying the technique (Fox 2006b, Abdollah 2003, Rosenfeld 2005, KTVO-TV 1999).

According to sworn testimony by Dr. William Iacono, an independent expert unaffiliated with Dr. Farwell who has conducted extensive research in the area, the science underlying brain fingerprinting has been published in hundreds, perhaps thousands, of articles in the scientific literature, and the specific application of this science in detecting information has been published in about 50 studies (Harrington v. State 2001). (For more information on the science and its acceptance in the scientific community, see P300.) Although the science is well established, opinions among scientists and others on the social policy question of how and when this science should be applied vary widely (Fox 2006b, Abdollah 2003). Dr. Farwell's decision to apply this science in bringing criminals to justice and freeing innocent suspects (Harrington v. State 2001) is controversial (Fox 2006b, Abdollah 2003, Dale 2001, ABC Good Morning America 2004, CBS 60 Minutes 2000). Various other attempts to apply this science in the detection of concealed information have varied in accuracy and efficacy, depending on the scientific procedures used (Harrington v. State 2001, Farwell 2012).

Farwell and colleagues (e.g. Farwell & Smith 2001) as well as other, independent scientists who have precisely replicated Farwell's research or used similar methods (e.g., Iacono and colleagues, Allen & Iacono 1997), have consistently obtained error rates of less than 1% in both laboratory and field conditions (Farwell 2012, Farwell et al. 2012).

Different scientific methods, however, have yielded different results. In P300-based tests using different experimental methods, different brain responses, different stimulus types, different data collection methods, different analysis methods, and different statistics from those used in Farwell's brain fingerprinting, Rosenfeld reported accuracy rates close to those obtained by chance, even without countermeasures (Rosenfeld et al. 2004). Moreover, Rosenfeld's alternative technique proved susceptible to countermeasures (Rosenfeld et al. 2004). (For scientific and methodological differences between Farwell's brain fingerprinting and Rosenfeld's alternative technique, see Farwell & Smith 2001, Farwell 2012, and Farwell et al. 2012.)

Controversy has arisen over the best explanation for the fact that Farwell and others who use similar scientific methods have consistently achieved less than 1% error rate (or in fact 0% error rate) (Farwell 2012) and high statistical confidences (Farwell et al. 2012), while Rosenfeld's alternative method yielded more than ten times higher error rate, sometimes as low as chance (Rosenfeld et al. 2004), as well as statistical confidences averaging chance (50%) for subjects lacking the relevant knowledge tested.

Farwell, FBI scientists Drew Richardson and Sharon Smith, and other brain fingerprinting experts claim that one cannot necessarily expect to obtain the same accuracy as brain fingerprinting without following standard brain fingerprinting scientific protocols or similar methods, that Rosenfeld's failure to achieve accuracy rates comparable to those of brain fingerprinting is the result of the substantial differences in scientific methodology between his alternative technique and brain fingerprinting, and therefore the fact that Rosenfeld's alternative technique is admittedly inaccurate and susceptible to countermeasures (Rosenfeld et al. 2004) is no reflection on brain fingerprinting (Farwell & Smith 2001, Farwell 2012, Farwell et al. 2012).

Proponents advocate continuing the use of brain fingerprinting to bring criminals and terrorists to justice and to free innocent suspects, while at the same time more research is continuing. Dr. Farwell and former FBI scientist Dr. Drew Richardson are among the scientists who advocate continuing the use of brain fingerprinting in criminal investigations and counterterrorism, without delay, as well as ongoing research on the technology (Farwell 2012, Farwell et al. 2012).

Dr. Farwell was interviewed by TIME magazine after he was selected to the TIME 100: The Next Wave, the 100 innovators who may be "the Picassos or Einsteins of the 21st Century." He said, "The fundamental task in law enforcement and espionage and counterespionage is to determine the truth. My philosophy is that there is a tremendous cost in failing to apply the technology." (Dale 2001)

Critics of brain fingerprinting claim that the inaccuracy and susceptibility to countermeasures of Rosenfeld's alternative technique also cast doubt on all P300-based information-detection techniques, including brain fingerprinting (Rosenfeld 2005). Critics agree with proponents that ongoing research on brain fingerprinting is valuable and desirable (Fox 2006b, Abdollah 2003). Unlike proponents, however, critics advocate a discontinuation of the use of brain fingerprinting in criminal and counterterrorism cases while this research is continuing (Fox 2006b, Abdollah 2003).

Proponents of the continued use of brain fingerprinting in criminal and counterterrorism cases cite the peer-reviewed research on the accuracy of brain fingerprinting in the laboratory and the field, the fact that it has been ruled admissible in court, the vital counterterrorism applications, and the benefits of bringing criminals such as serial killer JB Grinder to justice and freeing innocent convicts such as Terry Harrington. They emphasize the established science, the proven accuracy of brain fingerprinting when practiced according to standard brain fingerprinting scientific protocols, and the fact that brain fingerprinting is voluntary and non-invasive Farwell 2012, Farwell et al. 2012. They advocate continuing to use brain fingerprinting in criminal investigations and counterterrorism while research on the technique continues (ABC Good Morning America 2004 ABC-TV Good Morning America: Charles Gibson interviews Dr. Lawrence Farwell, CBS 60 Minutes: Mike Wallace interviews Dr. Lawrence Farwell, Farwell 2012.

Critics cite the inaccuracy and susceptibility to countermeasures of Rosenfeld's alternative technique, and suggest that this casts doubt on brain fingerprinting as well (Rosenfeld 2005). They emphasize the uncertainty of applying new technology while it is still being researched, and advocate discontinuing the use of brain fingerprinting in criminal and counterterrorism cases until more research has been completed (Fox 2006b "Brain Fingerprinting Skepticism", Abdollah 2003 "Issues: Brain Fingerprinting").

Extensive criticism of brain fingerprinting is contained in Rosenfeld 2005. Dr. Farwell's brief response is contained in a peer-reviewed paper published in Scientific Review of Mental Health Practice, Farwell 2011a "Brain Fingerprinting: Corrections to Rosenfeld". A more comprehensive version of this paper that contains extensive documentation and references to independent sources where the facts can be verified is "Brain Fingerprinting: Comprehensive Corrections to Rosenfeld in Scientific Review of Mental Health Practice" (Farwell 2011b). These issues are reviewed in more detail, with reference to all research published to date in English, in Farwell 2012.

Those personally affected by brain fingerprinting have expressed divergent views as well, particularly on the issue of delaying the application of brain fingerprinting in criminal cases. Terry Harrington, for whom brain fingerprinting provided exculpatory evidence that was ruled admissible in court (Harrington v. State 2001, Farwell & Makeig 2005), and who was subsequently released from prison after serving 24 years for a murder he did not commit, has advocated continuing to apply brain fingerprinting in criminal cases while the research continues (CBS 60 Minutes 2000).

See also[edit]


  • Allen J.J.B. and Iacono W.G. (1997). "A comparison of methods for the analysis of event-related potentials in deception detection." Psychophysiology 34:234-240.
  • CBS 60 Minutes: Mike Wallace interviews Dr. Lawrence Farwell, December 10, 2000.
  • Dale, S.S. (2001). "THE BRAIN SCIENTIST: Climbing Inside the Criminal Mind." TIME Magazine, Nov. 26, 2001, pp 80-81.
  • Denno, Deborah (December 2002). "Crime and Consciousness: Science and Involuntary Acts". Minnesota Law Review 87: 269–389 [332]. 
  • Druckman, D. and Lacey J.I. (1989). Brain and cognition: some new technologies. Washington, D.C.: National Academy Press.
  • Erickson, M. J. (2007). Daubert's Bipolar Treatment of Scientific Expert Testimony -- From Frye's Polygraph to Farwell's Brain Fingerprinting.’’ Drake Law Review 55’’, 763-812.
  • Farwell L.A. (1992a). "The brain-wave information detection (BID) system: a new paradigm for psychophysiological detection of information" (unpublished doctoral dissertation). Urbana-Champaign (IL): University of Illinois.
  • Farwell, L.A. (1992b). "Two new twists on the truth detector: brain-wave detection of occupational information." Psychophysiology 29(4A):S3.
  • Farwell L.A. (1993). "Brain MERMERs: detection of FBI Agents and crime-relevant information with the Farwell MERA system." Proceedings of the International Security Systems Symposium, Washington, D.C.
  • Farwell, L.A. and Donchin E. (1986). "The brain detector: P300 in the detection of deception." Psychophysiology 24:434.
  • Farwell, L.A. and Richardson, D.C. (2006a). "Brain Fingerprinting in Field Conditions," Psychophysiology, 43:5 S37-S38
  • Gaillard A.K.W. and Ritter W. (1983). Tutorials in event-related potential research: endogenous components. Amsterdam: North-Holland.
  • Harrington v. State, Case No. PCCV 073247. Iowa District Court for Pottawattamie County, March 5, 2001.
  • Harrington v. State. 659 N.W.2d 509 (Iowa 2003).
  • [ "Statement of the Iowa Attorney General's Office on Supreme Court Decision re Terry Harrington"].
  • Moenssens, A.A., (2002) Brain Fingerprinting—Can It Be Used to Detect the Innocence of Persons Charged with a Crime? UMKC L. Rev. 70, 891-920..
  • Picton T.W. (1988). Handbook of electroencephalography and clinical neurophysiology: human event-related potentials, Vol. 3, Amsterdam: Elsevier.
  • Rosenfeld, J.P., Soskins, M., Bosh, G. and Ryan, A. (2004) "Simple, Effective Countermeasures to P300-based Tests of Detection of Concealed Information" Psychophysiology, 41 pp 205–219 (PDF)
  • Slaughter v. State, No. PCD-2004-277 (Okla. Ct. of Crim. App., April 16, 2004)
  • United States General Accounting Office Report to the Honorable Charles E. Grassley, U.S. Senate. INVESTIGATIVE TECHNIQUES: Federal Agency Views on the Potential Application of ‘Brain Fingerprinting,’ October 2001.
  • Vrij, A. (2008). Detecting lies and deceit: Pitfalls and Opportunities, 2nd Ed.. Chichester, England: Wiley.
    (See in particular Table 12.2, Table 12.3 and Table 12.5 for GKT accuracy rates, and Box 12.3 starting page 361 for a discussion of Brain Fingerprinting).

External links[edit]