Fifth, a confident witness is more persuasive than a hesitant one.¹⁵ Acting confidently, even passionately helps establish credibility. One study found that jurors are twice as likely to trust a confident expert over an uncertain or unsure expert¹⁶ or even three times as much.¹⁷

Certainty has its persuasive advantages— and its pitfalls. Arrogant experts rarely gain credibility. Arrogance strikes jurors as annoying and possibly rigid and single-minded in their scientific work. In fact, studies show that confident and arrogant demeanors can be culturally-sensitive behaviors. Women who act like the legal system thinks they should act when they file sexual harassment claims are more likely to be believed.¹⁸ One’s assessment of the “right” demeanor of “virtuous” women is culturally dependent. Right or wrong, we often assess others’ credibility by our personal standards.

In fact, culturally-sensitive testimony in general is most likely to be interpreted as more persuasive. ¹⁹ A classic example is looking a person in the eye. Many Westerners expect persuasive speakers to look them in the eye. However, lowering of the eyes in some cultures, including Native American and many Eastern cultures, is a sign of respect and civility. Similarly, the feet in Middle Eastern cultures are a sensitive part of the body. Showing the soles of one’s feet to another is a grave insult. Offending jurors is unlikely to help them be good listeners.

Demeanor Evidence and Persuasive Forensic Testimony
The following are suggestions for forensic scientist to consider when testifying. This brief inventory flows from legal and scientific research on the brain and in juror research. These can be used alongside with the suggestions by Ashlock noted in Forensic Magazine²⁰ and are not intended to be exhaustive.

1. The expert is his or her testimony. Jurors do not discriminate between the demeanor of witnesses and their testimony.²¹ The content of testimony and the process of that testimony comes whole and intact to the juror’s attention. We instinctively and pervasively look for clues of credibility in another’s demeanor. Forensic scientists who take seriously how they testify just as much as what they testify about are the most effective witnesses. The Melendez-Diaz case underscores how seriously the law takes demeanor evidence. Valuing the role of demeanor evidence is the first lesson in effectively cultivating it.

2. Forensic scientists need to act like their jury testimony begins the second they enter the courtroom. Because it does. The jury assesses their testimony as soon as they see them enter the courtroom. Experts should be ready to testify in court the instant they are called by the bailiff or enter the deposition room. They say that General George S. Patton put on his “war face” when meeting with his soldiers and other officers during battle. Forensic scientists should likewise put on their “forensic faces” as soon as they enter the courtroom or are deposed. It should be a courteous face, professional, but expressive, even assertive. Their “forensic face” expresses eagerness, even excitement over explaining and sharing their research and conclusions.

3. Passion is good. Propaganda is not. Jurors want to see that the expert cares about his or her testimony, but don’t like robotic, bored, or pro forma answers.²² Firm and assertive testimony will inject persuasive inflection and emphasis into the tone, vocabulary, inflection, and cadence of testimony. Yet, rigid, arrogant, and rote testimony, accompanied by a raised voice, arm-waving, or pointing is both distracting and appears pre-packaged or pre-arranged.²³