top of page
  • Robson Crim

The Court's Flawed Reliance on Demeanour Evidence - Seth Lozinski


Demeanour evidence has long been established within the legal system as a measure for triers of fact to assess the credibility of a witness. The role of demeanour evidence and its relationship to trial fairness was solidified by the SCC majority judgement R v N.S., which has been heavily cited since the decision in 2012.[1] Although demeanour evidence is now acknowledged as an area of law that is fraught with danger, it is still considered a valuable tool in maintaining trial fairness.[2] I aim to demonstrate that the use of demeanour evidence does not align with its alleged purpose, and in fact may impede upon trial fairness rather than maintain it. I would further assert that the added warnings highlighting the potential risk of relying too heavily on demeanour evidence do not mitigate harm to the extent that justifies its frequent usage in the courtroom.

R v Falconer and Falconer

In R v Falconer and Falconer (NBQB), the merits of demeanour evidence were heavily considered.[3] This appeal was allowed on the grounds that the trial judge erroneously believed she was unable to utilize demeanour evidence to assess the credibility of a witness.[4] Justice Ferguson found that this error was severe enough to impact the outcome of the trial and ultimately agreed with the defence counsel’s assertion that the ability to observe a witness’s demeanour was crucial to a fair trial.[5]

Throughout his analysis, Justice Ferguson relied on jurisprudence to iterate the need to consider demeanour evidence. The cited judgements highlighted claims that non-verbal communication can provide the cross-examiner with valuable insights that may assist in getting at the truth.[6] It was further outlined that change in witness demeanour can be highly instructive, and that there is a strong connection between the ability to see the face of a witness and a fair trial.[7] The majority in R v NS was also cited to underline the importance of demeanour evidence, finding that it is too deeply rooted in our criminal justice system to be set aside.[8]

This insistence that demeanour evidence correlates with trial fairness is persistent within Canadian jurisprudence, however, it is rarely critically examined. The citations used in R v Falconer and Falconer do not explain how demeanour evidence informs a credibility assessment nor do they provide any evidence that it in fact does so. I do not find the repeated reliance on demeanour evidence to be convincing in demonstrating its value in maintaining trial fairness. This frequent reliance simply demonstrates a perpetual misconception on the part of the court in its ability to accurately assess demeanour and apply that assessment to determine a witness’s credibility.

Risk of Bias

In making his judgement, Justice Ferguson did acknowledge the risks of weighing demeanour evidence too heavily when assessing credibility, as it is particularly prone to stereotype and bias.[9] This is because judgements made based on a demeanour will more negatively impact a marginalized individual, as they are more likely to comport outside the expectations of a trier of fact. This can lead to false assumptions rooted in the oppression of vulnerable individuals due to classifications such as race, gender, and class.

A key example of prejudice within demeanour evidence is the impact of a witness’s disability. A diagnosis of neurodivergence often involves a reluctance to make eye contact, monotone expression, and difficulty sitting still.[10] Such body language and audible cues may create an assumption of nervousness or lack of credibility. Health conditions such as stroke or paralysis similarly create issues in assessing demeanour, as they impact facial expression, speech, and body language. This is also an issue for witnesses with mental illnesses, such as PTSD, which could result in a limited ability to emote, or conversely, a heightened emotional state. Each of these examples may negatively affect the perception of the trier of fact.

Race is another major factor; research has established that members of visible minority groups may be especially nervous when testifying for fear of being judged against a negative stereotype.[11] Similarly, it has been documented that innocuous behaviour has been interpreted by triers of fact as suspicious simply based on the race of the individual.[12] There may also be cultural differences which impact demeanour and how it is assessed, including differences in eye contact, body language, and clothing. This is particularly pertinent for witnesses testifying in a second language, as this could lead to nervousness, hesitancy, and increased stress, which will then impact a trier of fact’s assessment of their credibility.

To mitigate the impact of such biases on trial outcomes, courts will often iterate the risks of using demeanour evidence and affirm that demeanour alone should not be determinative in assessing a witness’s credibility.[13] However, this is insufficient, as bringing attention to the inherent risk of prejudice does not inform the trier of fact of the existence of their own prejudice. This does not address the risk of unconscious bias, as one must be aware of their prejudicial treatment of a witness to mitigate the impact of such treatment. In that case, rather than a warning of the risk of bias when assessing demeanour, the trier of fact will require education to bring awareness to their particular biases and how those biases impact their judgement of a witness.

Lack of Scientific Basis

Even without considering the prejudicial risk in assessing credibility through demeanour, I would argue that demeanour evidence is not a useful tool in the courtroom. In R v NS, the majority stated that scientific exploration of the importance of seeing a witness's face to cross-examination and credibility assessment may enhance or diminish the force of the arguments made in the decision.[14] Such scientific exploration has now materialized, and the findings should not only diminish the force of the reasoning upholding demeanour evidence but should diminish its usage altogether. Scientific studies persistently illustrate the inherent inaccuracy of utilizing demeanour evidence to assess credibility. Individuals, including lawyers and triers of fact, are not skilled at detecting deception.[15] Even with further training, it is not clear that demeanour would be an effective way to assess credibility, as one study found that experts were able to detect deceit in 55.51% of cases compared 54.22% of cases for a layperson.[16] It seems that training provides a modest increase in accuracy, while accuracy levels remain low, only slightly higher than the 50% chance a trier of fact has in guessing correctly whether a witness is being truthful.

Such research continues to refute the court’s assertion that it is well-equipped to measure credibility based on demeanour. One study analyzed 88 cues to determine deception and found that 65 (73.86%) had low success and 21 (23.86%) had low to moderate success in detecting deceit.[17] A second study found that excluding hand movements, physical cues related to deceit were imperceptible to the trier of fact. While perceptible, hand movements are equally problematic as they have the opposite effect of what is assumed: the number of hand movements decrease when lying — a finding that counters beliefs held by both legal experts and the public.[18]

It is evident that the legal system’s assumption that demeanour plays even a small role in assessing credibility is unfounded and disproved through scientific investigation. This begs the question, why hasn’t this issue been revisited? Demeanour evidence has been utilized in at least 2265 criminal cases in Canada in the last three years and the dissenting opinion in R v N.S. is often the reference used to caution its overuse.[19] In this dissent, Justice Abella clarified that while demeanour evidence is an important consideration in maintaining trial fairness, it does not weigh more heavily than the need to protect a witness’s religious freedom.[20] This statement is deficient in adequately limiting the validity of demeanour evidence. I would go one step further to say that demeanour is not an important consideration, and no longer has a place in the courts. Given the risk of prejudice and the large body of scientific research disputing claims of its perceived value, the use of demeanour evidence within the legal system should be resolutely challenged and overturned.

[1] R v S (N), 2012 SCC 72 [2] R v White 2011 SCC 13 at para 41. [3] R v Falconer and Falconer, 2020 NBQB 70. [4] Ibid at para 26. [5] Ibid at para 24. [6] Ibid at para 49. [7] Ibid at paras 49, 50. [8] Supra note 1 at para 27. [9] Supra note 3 at para 48. [10] Lim A, Young RL, Brewer N, “Autistic adults may be erroneously perceived as deceptive and lacking credibility” (2022) 52:2 Journal of Autism and Developmental Disorders at 490. [11] Rand JW, “The Demeanor Gap: Race, Lie detection, and the Jury” (2000) 33(1) Connecticut Law Review at 76. [12]James Chalmers, Fiona Leverick & Vanessa E. Munro, “Handle with care: Jury Deliberation and Demeanour-based Assessments of Witness Credibility” (2022) 26:4 The International Journal of Evidence & Proof. [13] R v Rhayel, 2015 ONCA 377 at para 85. [14] Supra note 1 at para 44. [15] Supra note 12. [16] Ibid. [17] Brent Snook, Meagan McCardle, Weyam Fahmy & John C. House, “Assessing Truthfulness on the Witness Stand: Eradicating Deeply Rooted Pseudoscientific Beliefs about Credibility Assessment by Triers of Fact” (Sept 2017), online (pdf): [18] Lucy Akehurst et al., ‘‘Lay Persons’ and Police Officers’ Beliefs Regarding Deceptive Behaviour” (1996) 10:6 Applied Cognitive Psychology 461. [19] In searching the terms “demeanour evidence” and “criminal law” across Canadian jurisdictions on Westlaw Edge in October 2022, 2265 cases were found. [20] Supra note 1 at para 109.


The views and opinions expressed in the blogs are the views of their authors, and do not represent the views of the Faculty of Law, or the University of Manitoba. Academic Members of the University of Manitoba are entitled to academic freedom in the context of a respectful working and learning environment.

  • Facebook Basic Black
  • Twitter Basic Black
bottom of page