Mask, mask on the wall, who is the fairest of them all? - Face masks and deception detection

A lie has no legs, they say. But what about face masks? One of the many changes brought by the COVID-19 pandemic is the decision by a growing number of jurisdictions to order litigating parties to wear facemasks during courtroom proceedings. Intuitively, one would think that the mandatory facemask makes the credibility assessment more problematic as it does not leave room for non-verbal cues. Instead, the situation is just the opposite!

COVID-19 has affected almost every aspect of our daily lives. Governments worldwide have taken various steps to control the spread of the virus, including recommending or ordering people to wear facemasks. The effect of this specific measurement on the justice system has received relatively little attention. One might think that requiring lawyers, witnesses, and other litigation parties to wear facemasks in the courtroom during a pandemic is a minor adjustment for the legal system. However, it is not, as it affects various social and cognitive processes influencing legal decision-making.

Deception detection and credibility assessment of the litigating parties might occur at several points throughout a trial, and the accuracy of these evaluations can directly affect trial outcomes. This blog post discusses how wearing medical face masks by witnesses and other litigation parties affects deception detection and assessing credibility in the broadest terms. The main concern here is that

any hearing in which a litigation party wears a mask for health-related reasons

does not allow the factfinder to evaluate the witness's credibility, and

the ability to detect any deceptive demeanor is compromised.

Notably, even though it might seem unfamiliar to lawyers practicing in continental law systems, the mask problem also has profound legal doctrinal implications in the U.S. Namely, the mask contravenes a central pillar of U.S.’ credibility jurisprudence based on the principle that a person's outward bearing is a crucial indicator and fundamental to assessing the credibility of witnesses.

Research addressing our specific question does not yet exist; thus, we cannot benefit from specific studies on COVID-19 and the psychology of the courtrooms. However, we can confidently rely upon one experiment that specifically examined mask-wearing in courtrooms (Leach et al., 2016) and formulate a well-informed view on the matter.

Before deep-diving into the findings of this specific research, it is noteworthy to mention that based on the pretty extensive deception literature, it is a pancultural belief that nonverbal behavior reveals deception (Global Deception Research Team, 2006; Vrij, 2008). Even though this popular belief derived from the work of Albert Mehrabian, carried out in the 1960s, I hypothesize that the once-popular T.V. series, ’Lie to me’ is also to be heavily blamed. My hypothesis is, of course, not empirically tested. But if we have a look at the synopsis of the show, we might suspect that there must be some truth to it: „About Cal Lightman, the world's leading deception expert who studies facial expressions and involuntary body language to expose the truth behind the lies”.

Anyway, people systematically believe that the body and face hold more signals to deception than verbal content.

This deeply rooted and profoundly flawed belief

has been labeled as demeanor bias (Hartwig & Granhag, 2015).

As a result, observers mistakenly believe they can trust their nonverbal judgments when assessing veracity. In contrast to this belief, the accuracy in determining veracity based on visual cues is 50.35% (Bond & DePaulo, 2006) which slightly differs from the chance level (50%). Relying on nonverbal behaviors when detecting deceit, relying on verbal content and verbal cues appears to be more effective (DePaulo et al., 2003; Vrij et al., 2019). Although nonverbal lie detection is widespread, the scientific literature suggests that it is unreliable to detect deception.

The above discussed pancultural belief are echoed in the decisions of judges in the United States, the United Kingdom, and Canada which ruled that witnesses may not wear the niqab—a type of face veil—when testifying, in part because they believed that it was necessary to see a person’s face to detect deception (please see Muhammad v. Enterprise Rent-A-Car, 2006; R. v. N. S., 2010; The Queen v. D(R), 2013).

In 2016, Leach et al. decided to empirically test if such rulings bore any relation to the truth and examined the specific assumption that niqabs interfere with lie detection:

Female witnesses were randomly assigned to lie or tell the truth while remaining unveiled or wearing a hijab (i.e., a head veil) or a niqab (i.e., a face veil). 232 students at a Canadian university (138 females, 94 males) first observed the testimonies as mock jurors and then answered the question if the witnesses told the truth. Notably, Leach et al. replicated the same experiment with subjects in Canada, the U.K., and the Netherlands.

The results showed that

the mock jurors were more accurate at detecting deception in witnesses

who wore niqabs or hijabs than those who did not wear veils.

Thus, there is no evidence that masks worn by the witnesses negatively impact credibility judgments. Fahmy et al. (2019) has recently replicated these findings: people’s perceptions of a mock sexual assault victim’s credibility were unaffected, regardless of whether she wore a face-covering – either a niqab or a balaclava – or not.

Ironically and pretty counterintuitively,

the researchers' results suggest that the opposite could occur.

Niqabs should minimize the amount of information available to observers and prevent them from basing their lie detection decisions on misleading facial cues. In turn, the veiling of the witness might force observers to attend to sources of information that are more diagnostic of deception, such as verbal content (Vrij, 2008). Simultaneously, having witnesses remove their masks to testify might, thus, have the unintended effect of hindering deception detection.

Even though the above-discussed research did not specifically address the medical face masks, the two subjects (medical facemasks and niqabs) seem to be interchangeable.

In this spirit, we can conclude that

medical face mask-wearing

will not hamper the factfinders’ deception detection abilities.

If judges can hear the verbal content well, they may even become better at detecting deception if they pay more attention to the verbal cues, which may result from mask-wearing in the courtroom.


Cheat sheet for busy lawyers


Less Is More? Detecting Lies in Veiled Witnesses


Year of publication

Theoretical/ Conceptual Framework

Research Question(s)/ Hypotheses



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