Edited by: Andrea Szymkowiak, University of Abertay Dundee, UK
Reviewed by: Elliot Berkman, University of Oregon, USA; Luca Sammicheli, University of Bologna, Italy; Federico G. Pizzetti, Università degli Studi di Milano - Dipartimento di Studi Internazionali, Giuridici e Storico-Politici, Italy
*Correspondence: Elena Rusconi, Department of Security and Crime Science, University College London, 35 Tavistock Square, London, WC1H 9EZ, UK e-mail:
This article was submitted to the journal Frontiers in Human Neuroscience.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Following the demise of the polygraph, supporters of assisted scientific lie detection tools have enthusiastically appropriated neuroimaging technologies “
In recent years researchers in cognitive neuroscience have started to investigate the neural basis of complex mental processes including moral beliefs, intentions, preferences, self-knowledge, social interactions, and consciousness. Influential neuroscientists are introducing the idea that our traditional notions of crime and punishment (and the laws built upon them) should be challenged, and if necessary modified, to make them more
Despite all these concerns fMRI is already being advertised as a scientifically proven lie detector by private companies having strong links with academia (see No Lie MRI—
But firstly in the following two sections we take a brief look at the basics of this technique in order to gauge an impression of what types of evidence fMRI currently may and may not be able to provide. For although most neuroscientists would agree that fMRI should not be used as a lie detector, especially within its current form (e.g., Grafton et al.,
fMRI is one of the most popular measurement techniques in cognitive neuroscience. It has been in use for about 20 years and is qualified as
As implied by its name, fMRI makes use of strong magnetic fields to create images of biological tissue. Depending on the
Central to cognitive fMRI studies are the concepts of differences and similarities between maps of
When evaluating fMRI evidence, with an eye on applying it to a real-world problem, it is important not only to be aware of basic experimental design principles but also of the peculiar requirements of the technique and its limitations (Spence,
The outcome of data analysis is a function of a series of consensus-based decisions, including options and parameters chosen for realignment, normalization, and smoothing, statistical models for analyses, and the associated correction criteria that can be more or less conservative. Finally, strategic decisions may guide choice of the evidence that will find its way in the final report on a peer-reviewed journal. Although raw data may be requested by anyone for further analyses, most readers will exclusively rely on the information provided in a polished report. Furthermore, in very competitive scientific environments there is no incentive for investigators to try and replicate their own findings as journals typically promote the publication of novel designs rather than replications (e.g., Giner-Sorolla,
In summary, protocol design determines how fMRI evidence can be interpreted, full compliance is required from participants, and the final evidence reflects choices, assumptions and data transformations based on current scientific standards and consensus criteria but also on publication strategies. Finally, not everybody can undergo fMRI. So the question remains, can its potential contributions as a lie detector outweigh its intrinsic limitations?
Many people believe they are very good at detecting deceit and that certain signs give away when somebody is lying: liars would talk too much and tell stories far more elaborate and detailed than required by the context; they would never gaze interlocutors straight in the eyes or would stare at them too intensely; or they would cross their arms or their legs; or a combination of behaviors (e.g., Houston et al.,
Conversely, the ability to lie develops spontaneously (it is typically absent in children with neuro-developmental impairments, like autism). Lying is fundamental to healthy behavior, as shown by the disastrous social interactions of patients with orbito-frontal lesions. Indeed some of these patients become notoriously tactless—which in a final analysis can be achieved by always being completely frank and honest. The literature on orbito-frontal patients suggests in turn that the ability to lie depends on the integrity of localized neural circuits (e.g., Damasio,
Recent attempts have been made with fMRI to specify the neural correlates of lying or deception (see Christ et al.,
Within a basic cognitive neuroscience perspective, fMRI research on deception can indeed aspire to provide correlation maps that possibly reflect the difference between deceitful and truthful responses. In order to obtain knowledge about the anatomo-functional substrates that are causally related to lying, and disambiguate potentially spurious activations, evidence would need to be collected with complementary techniques (e.g., with neurological lesion or non-invasive brain stimulation studies). fMRI is thus useful inasmuch as it hands over to techniques with complementary inferential power a map for (1) identifying cortical networks that play a necessary role in deception, and (2) testing their role by directly manipulating an individual's ability to deceive. This information could then feed back into fMRI maps and enable the identification of the most relevant correlates of lying for applicative purposes. The ability to establish causal links between brain substrates and behavior resides in the fact that the functionality of the brain tissue underlying stimulators can be temporarily modulated (e.g., see ; Nitsche et al.,
As a final point it is worth remembering that in basic research a participant's compliance with instructions is almost taken for granted as there is no rational reason why a participant might benefit from not following them. Quite the opposite situation may arise in a criminal forensic setting however, whereby it is not difficult to imagine that either intentional (e.g., adopting countermeasures) or non-intentional (e.g., due to alterations in one's emotional state) factors may lead to inconclusive results. In this respect, a recent study by Ganis et al. (
Legal systems are not new to influences from the cognitive neurosciences. For example, admissible MRI evidence showing the absence of frontal lobe maturation in the brains of teenagers contributed to the elimination of the death penalty for minors in some US states (frontal lobes are causally implicated in decision-making and the control of impulsive reactions; e.g., Damasio,
Despite this final fact, in 2006 two private bodies
Within this and the following sections we summarize and bring together the multitude of hurdles which need to be overcome before fMRI can ever be successfully integrated into criminal trials. Our discussions are primarily restricted to the English common law system of adversarial justice as applied throughout the United Kingdom, the United States, and Australia amongst others, as opposed to the continental European mixed adversarial-inquisitorial civil law systems. This decision is based on the particular nature of adversarial trials, with its competing prosecution and defense counsels who in turn can engage the services of competing expert neuroimaging witnesses, which may exacerbate some of the issues surrounding fMRI evidence discussed herein.
Legally, for scientific evidence to be admissible in criminal trials it must meet the legal standards as set down in the relevant jurisdiction, be these common law requirements such as either the test under
Within the specific constraints of the criminal law we can comprehend scientific evidence as being reliable if, amongst other things: the methods and results are both consistent and consistently applied; the accuracy of results meets an acceptably high standard while both false positives and false negatives are minimized; what practitioners
From the published fMRI literature it unavoidably emerges that fMRI technology has not reached this Assumptions and inferences underlying fMRI processes and technologies need to be confirmed (or dispelled) so as to give credence to the scientific claims being made. Cognitive neuroscience, for example, assumes that complex thoughts have a physical counterpart that is both accessible and interpretable with technologies such as fMRI (Erickson, To achieve internal validity, it needs to be conclusively determined that what is being measured is actually evidence of deception and not unrelated cognitive processes, and this needs to be determinable for each and every response given by every future individual undergoing fMRI questioning when operational. Contrary to public expectations lie detectors like fMRI are not The question of individual differences affecting fMRI results needs to be answered. The importance of this issue for a technology seeking both legitimacy and broad application cannot be underestimated. Neuroimaging devices need to be able to identify and correct for variances in individuals' brains and not operate on shared but unproven assumptions that all or most brain's process lies similarly (Ellenberg, The question of whether subjects or questioners can manipulate the fMRI baseline or response data needs to be addressed. To measure neurophysiological changes in the brain, neuroimaging devices must be able to create a reliable baseline against which comparisons can be formed. In this regard fMRI depends upon the cooperation of the subject and is highly vulnerable to countermeasures (e.g., Ganis et al., The subjectivity inherent in fMRI analysis algorithms needs to be acknowledged and these algorithms opened up for scrutiny. It has been claimed that fMRI output is superior to previous assisted lie detection methods partly because of the automated interpretation of results with computer algorithms which reduce the risk of human error by minimizing experimenter bias and subjectivity (Bilz, We need to determine the percentage of the population who for various reasons are unable to undertake an fMRI, as well as the nature of those reasons. fMRI is highly sensitive to movement, requiring subjects remain virtually motionless for long periods of time during questioning for the slightest head movement can wreck the resulting image. According to a review by Alexander ( Questions over the methodological validity of past and future fMRI studies must be answered. Many of the fMRI trials to date have compared group differences rather than individuals, and the few accuracy levels reported range between 78 and 90%. This discrepancy within detection rates counts against fMRI gaining admissibility within criminal trials and will not be remedied until more studies are published for peer review (Gerard, To attain external validity, experiments need to be applicable beyond highly controlled laboratory settings to confrontational, emotional “high-stakes” criminal justice situations. Criminal investigations and trials are confrontational and may represent high personal stakes for those involved. This will affect the individuals' mental state and underlying neurological processes (see e.g., Sip et al.,
According to skeptics the enthusiasm for brain imaging and related “mind reading” applications largely overestimate its current ability to identify unique neural correlates of complex mental functions such as lying (but see Haynes and Rees,
In summary, while fMRI may be a useful research tool in combination with other techniques to clarify the mechanisms involved in lying, and its degree of sensitivity and specificity in lie detection may be higher than that of the polygraph, most scientists currently agree that fMRI research evidence is still weak and lacks both external and construct validity (Spence,
Since the 1920s proponents of assisted lie detection technologies have been predicting their inevitable acceptance by courts; first for polygraphs and now for neuroimaging technologies (Gerard,
Possible constitutional and human rights violations (illegal search, right to silence, freedom of thought, right to privacy, human dignity, right to integrity of the person, and protection of personal data):
Looking across various common law legal systems, a number of constitutional principles, and human rights conventions
The first set of issues is whether fMRI questioning constitutes a
Another set of issues is whether fMRI questioning undermines the right to silence and the right not to self-incriminate. Neuroimaging technology has the potential to undermine these rights if it can operate without the individual needing to speak. Within the United States, the Supreme Court has previously speculated that “the involuntary transmission of incriminating lie-detection evidence would violate a suspect's right to silence” (Simpson,
It must also be asked whether questioning in fMRI without consent engages Article 8 Right to respect for private and family life and Article 9 Freedom of thought, conscience and religion of the ECHR. Article 8(1) has been broadly interpreted in the past, and it is readily conceivable that processes which seek to determine the veracity of our statements by measuring neural activity will engage this right. The question will turn on whether or not police will be able to conduct questioning in fMRI under the Article 8(2) qualifications of national security, public safety, and crime prevention, and what protections will needed to ensure proportionality. The answer to this might well be tied with Article 9, for to allow the state to access thoughts without consent and knowledge may have a chilling effect on both individuals and society as they seek to exercise their freedom of thought. Courts may well-seek to impose stringent safeguards on neuroimaging technology to prevent both the overuse and misuse of them if they feel these rights are threatened.
Additionally a number of rights within the Charter of Fundamental Rights of the European Union (CFREU) may also prove challenging for fMRI use in court proceedings. Article 1
Finally Article 8 CFREU
Compelled questioning and covert surveillance:
The issues of compelled questioning and (as the technology develops) covert neuroimaging surveillance are ones which courts will be forced to face given the potentially profound impact covert surveillance of this nature will have on society as a whole. One of the concerns raised is the potential for authorities to use these technologies for
Probative value, unfair prejudice, and undermining the Province of the Jury:
For evidence (including scientific evidence) to be admissible in criminal courts it must be
However, probative value also refers to the
Supporters of neuroscience technologies consider concerns over the undermining of judges and juries as unfounded; rather neuroimaging evidence will simply make the predictions of veracity by jurors and judges more reliable (Pardo, Because even a highly reliable neuroscience test would not establish knowledge or lies directly, jurors would still need to play their traditional role in assessing it. In making these assessments, the jury would, for example, consider whether other evidence regarding credibility should override the test results, rendering the test conclusion unlikely. (2006: 318)
While this statement seeks to defend and support fMRI in criminal courts, it unwittingly demonstrates the danger that this technology will import unfair prejudice into criminal trials. To explain; by rightly accepting that even a highly reliable neuroimaging test does not directly establish knowledge or lies one must ask “what is the point of introducing evidence to a jury from a technology that cannot provide direct evidence as to the veracity of statements made but is still marketed and promoted as a scientifically accurate lie detector
Right to a fair trial:
Depending on how questioning in fMRI is conducted for criminal trials it can be argued that the fairness of trials will be placed at risk unless
Nevertheless, it is conceivable that fMRI evidence may become admissible solely as a defense instrument given that structural brain scans have already found acceptance and are widely admissible as mitigating evidence during sentencing proceedings. Indeed such use may help ensure a trial is ultimately fair. However, any attempt to extrapolate from this niche application such that fMRI evidence can be used throughout the entirety of the trial
Our discussion throughout has focused on the scientific, legal, and ethical hurdles facing those seeking to introduce fMRI evidence into trials as a means of assisting judges and juries in determining the veracity of statements made. Schauer (
The evaluation of fMRI accuracy in lie detection—in some cases claimed to be as high as 0.90—is indeed based on laboratory experiments conducted with compliant participants, which is unlikely to be true of most legal settings where non-compliance and the use of countermeasures would make its accuracy figure drop dramatically (e.g., Ganis et al.,
Neuroimaging in courts also raises the specter of potential constitutional and human rights violations. Questions arise as to whether or not such testing constitutes an illegal search as well as how it respects rights to privacy, silence, thought, and a fair trial are all engaged by this technology yet left unanswered. Unless the admissibility decision is taken out of the hands of the judiciary by politicians, which is itself a likely scenario, ultimately it will be for the courts to decide the fate of fMRI evidence in criminal trials. Given the range and depth of the legal and ethical issues identified in the earlier sections, the likely outcome will probably fall on a spectrum somewhere between outright rejection through to some form of restricted and regulated usage, as opposed to the highly unlikely scenario of
What we have not discussed within this paper are both the
From the
A final hurdle to the widespread introduction of fMRI testing is
Our societies have developed to both accept and respect an individual's right to keep secrets, and in so doing they do not seek to override human beings' evolved capacity to keep secrets, for a society where individuals are denied secrets is not a human society as we know it. The developers and proponents of fMRI testing must respect this fact and engage society in their research as it progresses. Otherwise they may find they successfully negotiate the frying-pan of scientific and technical challenges in perfecting fMRI testing only to be consumed by a fire of legal, ethical, social, and political opposition.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The authors would like to thank Roberto Cubelli for his comments on a previous version of the manuscript, the Editor and three Reviewers for their very constructive comments. This study was funded by EPSRC (grant number EP/G037264/1).
1A pulse sequence is the series of changing magnetic field gradients and oscillating electromagnetic fields defined by the user that allows the MRI scanner to tune on and create images sensitive to a target physical property. Different pulse sequences, for example, are used when collecting structural data and functional brain activations.
2The term “functional” refers to changes in brain function and regional levels of activation over time.
3fMRI is based on the difference in magnetic resonance signals from oxyhemoglobin and deoxyhemoglobin and builds on the fact that active brain regions tend to use more oxygen than relatively inactive regions. Soon after a brain region has been activated by a cognitive event or task, the local microvasculature responds to increased oxygen consumption by increasing the flow of new arterial blood (i.e., blood rich in oxyhemoglobin) to the region. As a consequence, the relative concentration of deoxyhemoglobin decreases, thus causing localized changes in the magnetic resonance signal. These changes are known as blood oxygenation level-dependent (BOLD) signal (Purves et al.,
4For a broad overview on other relevant testing paradigms—that can also be used in fMRI studies—we direct the reader toward Gamer (
5Internal Validity refers to the appropriateness of construct operationalization and of experimental design in order to test the hypothesis of interest. It guarantees that any obtained effects may be univocally attributed to the experimental manipulation. Clearly, the use of expensive and fancy techniques does not guarantee by itself that experimental results are meaningful and interpretable.
6In this context, the “construct of interest” is the brain fingerprint of lying.
7The difference in signal on fMRI images from different experimental conditions as a function of the amount of deoxygenated hemoglobin.
8The term “parieto-frontal” areas denotes brain regions in the parietal and frontal lobes. The parietal lobe is located on the posterior and dorsal surfaces of the cerebrum. The frontal lobe is the most anterior lobe of the cerebrum.
9In some states polygraph evidence is permitted when both the prosecution and defense agree to its admissibility, while in others such evidence cannot be admitted even when both parties would otherwise agree.
10The sources examined here are: the US Constitution (limited in application to US citizens within US territories), the European Convention on Human Rights (produced by, and applying to, the 47 member states of the Council of Europe, and overseen by the European Court of Human Rights), and the Charter of Fundamental Rights of the European Union (applicable to all citizens and residents of the 28 member states of the EU, this Charter enshrines a range of personal, civil, and social rights and existing conventions and treaties (including the European Convention on Human Rights) into EU law thus ensuring their legal certainty).
11Taken from the French Civil Code, Book I: People, Title I: The Civil Rights, Chapter IV: the use of brain imaging techniques.
12Both of the two commercial companies offering fMRI detection service specifically and deliberately promote their technologies as scientific lie detection tools and not as veracity probability enhancement tools; No Lie MRI claims their technology ‘represents the first and only direct measure of truth verification and lie detection in human history’ (see