Limitations of Brain Fingerprinting
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) and in a Law Enforcement Technology article (Simon 2005) as well as in Farwell's publications and patents (e.g., Farwell 1994, Farwell 1995a, b, Farwell & Smith 2001). 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, Simon 2005, Harrington v. State 2001). 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 (Simon 2005), 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, Simon 2005, PBS 2004).
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). 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. 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). 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, 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 MERMER technology, and to include the successful brain fingerprinting research at the FBI, CIA, and US Navy.
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