Significant Findings

We have examined several different aspects of legal decision-making and its repercussions. Below, we briefly highlight some of our significant findings. The original articles can be accessed by clicking on the citations provided.



Non-native Speakers
There are many legal contexts – such as at border crossings – in which a person might be interviewed in his or her non-native language. In a series of SSHRC-funded studies, we have been examining how variations in language proficiency affect deception and its detection. Thus far, we have found that:

  • Laypersons and police officers believed that non-native speakers would exhibit the same cues to deceit as native speakers, despite facing more challenges during interrogations (Leach et al., 2019).
  • Laypersons and police officers were less accurate when detecting the deception of non-native (vs. native) English speakers (e.g., Da Silva & Leach, 2013; Leach & Da Silva, 2013).
  • Observers tended to indicate that native speakers were telling the truth, but either exhibited no bias (e.g., Leach & Da Silva, 2013) or a lie bias (Da Silva & Leach, 2013) toward non-native speakers.
  • Deception detection might depend on the exact level of language proficiency exhibited by non-native speakers: observers were less able to discriminate between lie- and truth-tellers who were beginner English speakers than those who were intermediate or native English speakers (but not advanced English speakers; Elliott & Leach, 2016).
  • Observers’ familiarity with non-native speech did not mitigate proficiency effects (Leach et al., 2017).
  • Exposure to non-native speakers’ accents might be driving observers’ decision-making (Akehurst et al., 2018).

In a SSHRC-funded project, we tested assumptions underlying courts’ decisions in the U.S., U.K., and Canada (i.e., that women must remove their niqabs while testifying so that triers of fact can detect deception and ensure the fairness of court proceedings). We found that:

  • Contrary to judicial opinions, observers were better able to detect the deception of witnesses who wore niqabs (vs. did not veil; Leach et al., 2016).
  • Findings generalized to observers in Canada, the UK, and the Netherlands (Leach et al., 2016).

Even very young children may be asked to serve as witnesses in court. Thus, it is critical to establish whether observers can detect children’s deception. We have examined this issue in early and middle childhood (i.e., 3- to 11-year-olds) and found that:

  • Younger children’s deceit was slightly more readily identified than that of older children (Leach et al., 2004).
  • Observers had difficulty discriminating between child lie- and truth-tellers (e.g., Lawrence et al., 2017; Leach et al., 2004).
  • Children’s deception was easier to detect if they had engaged in moral reasoning tasks or promised to tell the truth before being interviewed (vs. control; Leach et al., 2004).
  • Child lie-tellers who were instructed to maintain an experimenter’s gaze provided fewer details than truth-tellers; in turn, this facilitated observers’ deception detection (Lawrence et al., 2017).


Despite findings that deception detection is relatively poor overall, there exists a range in performance. We have examined this variability in deception detection from two major perspectives – indices of performance and individual differences – and found that:



  • Content experts (i.e., criminal justice experts and social scientists) conceptualized coercion differently from potential triers of fact (Kaplan et al., 2019).
  • Law enforcement officials estimated that the average interrogation lasted 1.6 hours, with the majority of suspects waiving their Miranda rights and providing self-incriminating statements (Kassin et al., 2007). Interrogations – which the majority of officers supported recording – were reported to almost always consist of physically isolating suspects in a small private room, identifying contradictions in suspects’ accounts, and attempts to develop rapport.


  • The presence of stolen property on a suspect improved showup accuracy, suggesting ensemble formation (Smith et al., 2013).
  • Viewing an eyewitness identification procedure (including biasing exchanges) did not improve jurors’ decisions (Beaudry et al., 2015).
  • Reviews of the state of the literature and discussions of contemporary controversies in the field revealed variability in the effectiveness of different types of lineups and directions for future research (Leach et al., 2009; Lindsay et al., 2009a; 2009b).


  • People who were reported to have been wrongly convicted of a crime were perceived as being more similar to convicted (guilty) criminals than average (innocent) people (Clow & Leach, 2015a).
  • The factors that led to the wrongful conviction affected stigma and decisions to help: individuals who had falsely confessed to the crime were stigmatized more than other exonerees (Clow & Leach, 2015b).