Prospects of functional magnetic resonance imaging as lie detector - Rusconi & Mitchener-Nissen (2013) - Article

What role can fMRI play in criminal courts? 

Functional Magnetic Resonance Imaging (fMRI) has been proposed as a possible tool for detecting both malignancy and deception in criminal courts. There are however questions with regards to its reliability as a lie detection tool according to scientific standards, as well as ethical and legal issues. 

What is fMRI?

fMRI records brain states in parallel with ongoing mental activity and/or behavior. It establishes a correlation, not causal, link. It uses strong magnetic fields to create images of biological tissue. The scanner can detect different tissue properties and distinguish between tissue types. They can see brain structural information (the static anatomy of the brain) and local changes in blood oxygenation within the brain over time (brain activity). 

How can lying be inferred from fMRI? 

BOLD stands for blood oxygenation level-dependent signal. In lie detection studies where fMRI is used, responses are evaluated in relative terms as the result of a contrast between two or more conditions (for example, maps of the BOLD signal of the participant lying are compared to the maps of the participant telling the truth). 

What are the limitations of fMRI when used to predict lying? 

Attention needs to be paid to scanner reliability and the technical skills of the staff. Control conditions need to be carefully matched to be able to isolate the construct of interest. Participants need to perform their tasks accurately and consistently. Their behavior should be monitored and recorded during the scanning session. In experiments that involve arousal or emotional stimuli, skin conductance, heart rate, and salivary hormones could also be monitored. 

How can lying be seen in the brain?

Attempts have been made to specify the neural correlates of lying with fMRI. Several studies have identified a network of parieto-frontal areas that are significantly more engaged when someone is lying. The results infer that lying requires extra effort compares to responding truthfully. This effort could be aimed at inhibiting the truth and/or coming up with an alternative response. Also regions in the limbic system have been associated with lying. 

Can fMRI be used in criminal courts?

Attempts are being made to use fMRI for legal proceedings, employment screening, national security investigations, and evidence in criminal courts. Legally, for scientific evidence to be admissible in criminal trials, it must meet the legal standards of the relevant jurisdiction. Scientific evidence needs to be relevant as well as reliable. 

When is scientific evidence reliable enough to be used in criminal courts?

Scientific evidence is reliable when:

• the methods and results are both consistent and consistently applied

• the accuracy of the results meets an acceptably high standard while both false positives and false negatives are minimized

• what is being measured what is believed to be measured

• the processes being measured are understood and agreed upon by scientists

• the scientific processes being used apply equally to all individuals regardless of internal and external traits and influences

Is fMRI reliable enough to be used in criminal courts? 

fMRI technology has not yet reached this reliability threshold and lacks both external and construct validity. These are the concerns:

• Assumptions and inferences underlying fMRI processes and technologies need to be confirmed. A cognitive ontology needs to be created, specifying the component brain operations that comprise specific mental functions. 

• It needs to be determined that what is being measured is actually evidence of deception and not unrelated cognitive processes (and it needs to be determined for every response given by every person). Suppressing natural tendencies is not a reliable indicator of lying, especially in the context of a trial. Also, in the context of a trial there may be other neurological processes (such as anxiety, fear), which are unrelated to deception, and may make it seem those areas of the brain are involved in lying. 

• Neuroimaging devices need to be able to identify and correct for variances in individuals’ brains and cannot assume that all brains “lie” the same. Many factors can be of influence, such as age, substance abuse, and mental disorders. 

• fMRI output is based on results with computer algorithms. However, algorithms are not purely objective. They reproduce all the subjectivity, bias, and assumptions of the programmers, and can introduce errors that bias results. 

• It needs to be determined which percentage of the population cannot undergo an fMRI (e.g. Parkinson, claustrophobia, metal pins). 

• Many fMRI trials have compared group differences, but also individuals need to be compared.

• To attain external validity, experiments need to be applicable beyond highly controlled laboratory settings to criminal justice situations, which can be confrontational and high stakes may be involved. It will affect the mental states of the individuals and the underlying neurological processes. Translational validation requires access to real-world situations with minimal interference and the possibility to derive an objective index of performance for deception detection. 

What are the legal and ethical issues?

What constitutional and human rights violations can be identified? 

• Illegal search (Does fMRI questioning constitute a search of the object and when will such a search be legally allowed? Will neuroimaging results be the same as other forms of physical evidence such as DNA?)

• Right to silence (Does a person’s brain activity exist independent of their will to remain silent, like DNA?)

• Freedom of thought and right to privacy

• Human dignity and right to integrity of the person (Is fMRI questioning without the person’s consent a violation of their human dignity?)

• Protection of personal data (Does fMRI data constitute personal data?) 

Why can compelled questioning and covert surveillance become an ethical issue? 

Potential authorities could use new technologies to question a person to determine if they have committed a criminal act in the past, without any pre-existing evidence or reasonable suspicion. This would undermine the presumption of innocence until proven guilty. 

What is probative value and how can it cause unfair prejudice?

The probative value of evidence can be identified as the extent to which evidence increases or decreases the probability of a fact in issue. Evidence to be admitted in criminal courts need to have probative value (be relevant). With regards to fMRI evidence the probative value is the extent to which it increases or decreases the subjective veracity probability of the accused’s statement (how it affects the factual probability that a person does or does not believe what they are saying). It is feared that this difference between lie detection and statement veracity will not be clearly explained to jurors, and that fMRI evidence will unduly influence and taint their deliberations. 

How can the use of fMRI in criminal courts influence the right to a fair trial?

It can be argued that if fMRI are ever introduced in the courtroom, that all parties should be subjected to pre-trial fMRI questioning, or the trial would not be fair. This has complications too, because not all parties may be capable of undergoing fMRI testing (for example when they are deceased). 

What are the operational and social barriers?

From the practical operational perspective there are many issues which require further examination:

• The cost of purchasing, staffing, and maintaining sufficient fMRI machines to provide for the national justice system

• The additional time and monetary costs fMRI testing will add to the criminal cases

• How fMRI testing can be used within adversarial systems of questioning and cross-examination based on earlier responses

• The lack of a courtroom-friendly portablefMRI system

• The algorithms that are used when interpreting fMRI response data

With regards to societal acceptability this technology still lacks public confidence and legitimacy. Our societies accept and respect an individual’s right to keep secrets and future research needs to investigate if the public will accept these new technologies. 

What can be concluded with regards to the use of fMRI in criminal courts?

fMRI is not capable of saying with certainty which brain areas are strictly necessary for lying. Evaluations are based on laboratory experiments with compliant participants and cannot be compared to real life situations. There are also issues of replicability and generalizability across conditions and participants. Until this science improves it will not meet the relevance and reliability thresholds for scientific evidence to be admitted in criminal trials.