His experiments on stereotypes regarding expert witnesses and their persuasiveness show that under some conditions, people pay attention to cues outside the evidence, “especially when the testimony is complex and difficult to understand”, McKimmie said.

In the experiments, participants heard exactly the same testimony from male and female witnesses on business-related cases involving automotive and perfume and cosmetic companies.

“They appear to rely on stereotypes regarding the generally accepted knowledge domains of men and women to help them decide whose testimony to believe or the weight they attach to it,” he said.

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The findings showed that people tend to place emphasis on the gender of the expert witness during decision making in a group.

Law practitioners are aware of these biases and implicitly use the effects of “culturally shared beliefs” to heighten the persuasiveness of their expert witnesses, McKimmie argued.

He suggested that there should mechanisms put in place to ensure jurors make the best decisions they can, suggesting screens for witnesses may help.

“The legal system places a lot of emphasis on being able to observe people giving testimony, but this may need to be reassessed if it makes it more difficult for people to pay attention to the testimony,” he said. “The way people look and talk is incredibly persuasive.”