Australian courts use “body language” to judge witness credibility

Nonverbal behaviour in the courtroom can significantly influence how judges assess the credibility of witnesses in their rulings. But is reliance on “body language” based on sound science?

Vincent Denault, an assistant professor in the School of Criminology at Université de Montréal, and Danielle Bozin of the School of Law at the Queensland University of Technology in Australia, examine the question in an article published in late September in the Journal of Forensic Psychology Research and Practice.

Denault and Bozin analyzed 602 cases heard in Australian courts between 1986 and 2020 and found 45 instances—31 at the trial level and 14 at the appellate level—in which judgments explicitly referenced a witness’s nonverbal behaviour, or “body language,” to assess their credibility.

“In a third of these cases, the courts referred to body language in vague and often general terms,” Denault said. “It’s like a black box filled with potentially dubious observations. We don’t know the basis for the judge’s conclusions. Did the judge think a witness was lying because they scratched their nose?”

The study reveals that Australian judges sometimes ascribe specific emotions to witnesses based on their body language. For example, one judge wrote that a witness “showed his agitation by raising his voice and in his body language.” In other cases, judges drew conclusions about a witness’s honesty based on their nonverbal behaviour.

The study also highlights the role of lawyers in either perpetuating or challenging these myths. In some cases, lawyers cited discredited lie detection cues, such as avoiding eye contact. On the other hand, others urged caution in judging the behaviour of witnesses, particularly Aboriginal witnesses.

Do the authors believe that the references to body language in legal decisions casts wider doubt on the basis of judicial rulings?

“The issue is understanding the factors that sway decision-makers,” Denault replied. “Our study provides a clear example of how the courts are influenced by pop culture.”

The authors point to research that has shown that “the relationship between nonverbal cues and deception is faint and unreliable.” The High Court of Australia itself has acknowledged “the fallibility of judicial evaluation of credibility from the appearance and demeanour of witnesses.”

So, in view of the science, using body language to judge a witness’s honesty is problematic. The situation is cause for concern.

What is to be done? “The solutions aren’t obvious because we are constantly influenced by nonverbal behaviour, often without realizing it,” Denault admitted. “The solution isn’t to eliminate nonverbal cues. That that wouldn’t necessarily lead to greater objectivity: there are also stereotypes and prejudices about the way people speak and the words they use.”

Denault believes education is the better approach. Judges and jurors should be made aware of the power of popular beliefs to help them avoid misinterpreting the behaviours they observe. He also recommends reducing the influence of nonverbal cues by highlighting other evidence when possible.

According to Denault, the implications of this research extend beyond Australia’s borders. Similar studies in Canada—including some of his own in Quebec—and the United States have revealed comparable issues, suggesting that this is a widespread phenomenon across legal systems.

He believes these findings are probably the tip of the iceberg. Further research is needed in this area, particularly on aspects of witness behaviour such as eye contact, tone of voice, hesitation and spontaneity, all of which are also surrounded by stubborn myths.

“Although it aspires to objectivity, the legal system is not immune to the influence of pop culture,” Denault concluded. “Our study underscores the critical importance of bridging the gap between scientific knowledge of nonverbal communication and judicial practices in order to ensure fair trials and rulings based on solid evidence rather than misinterpretations of nonverbal behaviour.”