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Why credibility needs to be assessed through a trauma-informed lense

By Anne-Marie Langan*

This is a summary of the article by Thor Paulson, Benjamin Perrin, Robert Maunder and Robert Muller entitled “Toward a Trauma-Informed Approach to Evidence Law: Witness Credibility and Reliability” (Paulson et al., 2023).

The article notes that the traditional approach of judges and juries in making findings of credibility does not align with what is now known due to scientific research about the impact of trauma on victims and puts into question some fundamental rules of evidence and instructions given to juries. Two traditional “tools” used to evaluate witnesses’ credibility, prior inconsistent statements and assessments of the demeanour of witnesses are particularly problematic in this regard as they do not account for the impact of trauma on memory formation and retention and that people's emotional reactions to trauma vary widely and sometimes are manifested in ways that are not traditionally thought of as being a trauma reaction, such as having a deadpan face while testifying about a traumatic experience. Also, the authors note that the high incidence of people who have experienced trauma (76.1% of Canadians) makes the issues they are raising about the traditional rules of evidence when it comes to credibility all the more relevant and important for us to address in order to ensure fairness.

Studies have shown that a traumatic experience can impact the manner in which we remember, particularly when it comes to episodic memories and autobiographical memories. Trauma can impact the manner in which we encode information because adrenaline and cortisol that are released after initially intensifying the memory thereafter impair the brain’s ability to form new memories resulting in “flashbulb memories” with lots of gaps. Trauma can also impact other physiological processes which can result in sensations, emotions, behaviour and conscious awareness being disconnected from their context in time and space. As well trauma victims often respond by dissociating from the experience which also can impact their ability to remember the entire event. There is the added difficulty that trauma can impact a person’s ability to sleep which is when our memories get consolidated and become permanent and can impact the retrieval of memories. As a result, traumatic memories are often “incomplete, are primarily visual, can lack context and a logical and chronological coherence" (Paulson et al, 2023, p.516). As a result, studies have shown that traumatic memories are less likely to be found credible, mainly “due to the positive correlation between richness of detail and perceptions of credibility and reliability” (Paulson et al, 2023, p.518). Sadly this new science about the impact of trauma on memory is at times being used against victims in court as a way to undermine their credibility by defense counsel.

There is the added dilemma that trauma is experienced far more frequently amongst traditionally marginalized groups such as First Nations, Inuit, Metis, LGBTQ2S youth, those who are homeless or precariously housed, people with substance use issues, people of lower socioeconomic status, immigrants and people of colour who already start with a disadvantage in credibility determinations due to negative stereotypes about them. Though not mentioned in the article women can also be included as belonging to a traditionally marginalized group membership stereotypes which often lead to not being found credible.

Traditionally courts and juries have interpreted discrepancies between what a witness stated outside of court and what they state on the stand under oath as pointing to a lack of credibility and/or reliability of their testimony. Given that most witnesses are interviewed before a court proceeding either in examinations for discovery if a civil proceeding or by police and at preliminary hearings in a criminal proceeding there is almost always some evidence available other than court testimony that can be used to “impeach” a witness’ credibility and/or reliability and is a tactic commonly used by lawyers due to its effectiveness. However scientific studies have found a weak relationship between inconsistencies and actual accuracy and have also found that 60.05% of witnesses provided additional information in a subsequent interview that was never divulged in the police interview. The authors note that judges rarely distinguish between inconsistent statements resulting from additional evidence and inconsistent statements resulting from contradictory evidence, and where the evidence is contradictory they rarely distinguish between contradictions about facts that are essential to the determination that a crime existed and facts that are incidental when making credibility determinations. Due to there being a high degree of deference by appellate courts when it comes to findings of credibility made by the judge hearing the actual evidence, any problems in the reasoning behind the determination are not likely to be considered on appeal.

When reviewing the relevant case law the authors note that on the whole where judges take into consideration the impact of trauma on a witness’ credibility without the benefit of expert testimony they will only find the witness credible where there is corroborating evidence to support it. There is a large debate about when it is legitimate or necessary to call expert evidence about the impact of trauma on memory. Generally, it is only advisable if the subject of the evidence is something that neither the judge nor jury are likely ever to have experienced themselves because otherwise they are supposed to rely on their experience and “common sense” in making determinations about credibility. Lately, some courts have taken “judicial notice” of the impact of trauma on memory which is reflected in comments in the case law about how victims of sexual assault can be presumed to have been traumatized, that trauma can cause memory lapses and that people can suppress memory due to trauma. However, this has not been applied by judges consistently and is not part of the instructions given to jurors in Canada.

The authors note that the HRTO in Joe Singer Shoes did a very good job of explaining the impact of trauma on memory and emphasized the “quality rather than the consistency” of the witness’ memory. This decision was upheld in divisional court and the HRTO credibility assessment was at issue in the appeal suggesting that this can be relied on as a precedent in cases where this becomes an issue. They also highlight that the UK’s model jury instructions do a much better job of addressing the issue of credibility by stating “inconsistencies in accounts can happen whether a person is telling the truth or no. This is because if someone has a traumatic experience such as the kind alleged in this case, their memory may be affected in different ways. It may affect that person’s ability to take in and later recall the experience” (Paulson et al., 2023, p.530).

Another related issue is how demeanour is used to assess credibility. Demeanour refers to anything other than words stated including tone of voice, emotional undertones, degree of enthusiasm or lack thereof, breathing rhythms, and degree of politeness. While it has long been accepted that a trier of fact cannot rely on demeanour alone, the authors suggest that this should not be considered at all given the multitude of stereotypes that can impact this very subjective assessment. Add to that the fact that trauma victims often have difficulty concentrating and become disoriented and confused when talking about their experiences which, in turn, can impact their demeanour. They also can get aggravated and angry, or dissociate and have a completely flat affect, all of which can easily be misinterpreted by those who do not have adequate training. Again the authors highlight that the UK Crown Court Bench Book specifically references that it is important not to bring any preconceived views as to how a witness in a trial should act or react and that “it does not follow that signs of distress by the witness confirms the truth and accuracy of the evidence given.” (Paulson et al. p. 541). The authors conclude that there is a need to reform evidence law to reflect a more trauma-informed perspective which will require further research such as how past trauma can impact a judge’s and jury’s perception of credibility and the impact on juries of testimony by witnesses who have experienced trauma.


A.B. v. Joe Singer Shoes Limited, 2018 HRTO 107 (CanLII), <>, retrieved on 2024-01-10

Paulson, T., Perrin, B., Maunder, R. G., & Muller, R. T. (n.d.). Toward a trauma-informed approach to evidence law: Witness credibility and Reliability. The Canadian Bar Review.

Anne-Marie Langan B.A., B.S.W., LL.B., LL.M. is the project lead for the sexual violence projects at Peterborough Community Legal Centre, including the SHAPE project which provides legal advice and education for those experiencing sexual harassment in the workplace and the Your Way Forward project which provides support for those who have experienced intimate partner sexual violence. These projects are both sponsored by the government of Canada. She can be reached directly at

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