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The Emotions That Prosecutors Elicit to Make Jurors Vote Guilty

Jurors experiencing “moral outrage” will be more likely to convict, and changes in technology are making this a bigger factor.


In May, an off-duty British Army soldier named Lee Rigby was murdered, in broad daylight, in what is likely the most incredibly brazen and baffling act of violence the neighborhood of Woolwich, London, had ever seen. Two men purposely ran over Rigby with their car, then got out and attacked him with knives and meat cleavers until he died. While many aspects of this shocking crime were initially a mystery, the actual sequence of events, at least, was clear—thanks to numerous perspectives and recording devices, including witness reports, CCTV surveillance video, a hand-written confession letter, and, most disturbingly, an on-the-scene, blood-covered confession delivered to a bystander’s video camera.

Rigby's alleged attackers are on trial now in the U.K. Both have admitted possession of a firearm but have pleaded not guilty to murder. It’s a little hard to imagine how that’s going to work for them, considering the amount of incredibly graphic visual evidence that jurors are faced with (most of which had already broadcast online in the British media immediately following the murder). As the BBC reported from the courthouse last week, “There were gasps in court as CCTV footage was shown.”

"When judges weigh the informational value versus the prejudicial value of the evidence, it is important to be very mindful that the negative emotions roused by emotionally disturbing evidence."

Even in cases less shocking, and cases with verdicts less inevitable, visual evidence is incredibly powerful. If jurors can see the defendant committing the crime, it’s common sense that they will convict, of course. In other cases, though, visual representations of the aftermath of a crime, and the damage done to the victims, can have another important impact, besides logic—that is, a purely emotional one. Jurors will be instinctually repulsed by seeing a bloody photograph. Even if they don’t know whether the particular defendants currently on trial were the people who caused the bloody scene, the sight of it will naturally stir the juror’s feelings. The best prosecutors know how to inspire those emotions strategically, and how to use them to their side’s advantage.

Recently, two psychologists teamed up to analyze and identify the emotions that have the most impact on the outcome of jury trials. They had participants in mock trials read scenarios and look at crime-scene evidence, and keep track of their feelings throughout the experiment. The researchers found that anger paired with disgust makes up the powerful mix of emotions that we often call “moral outrage.” The authors also concluded that this particular response—more than sadness, more than the desire for vengeance, more than any other emotion—is the one that most often brings jurors to vote to convict, and to be confident in those convictions.

“Humans intuitively understand what moral outrage is,” said Jessica M. Salernoo, co-author of the study, published in the journal Psychological Science. “However, researchers debate its emotional components. We wanted to investigate the relationships between anger and disgust since emotions tend to co-occur with each other.” Salerno and her co-author, Liana C. Peter-Hagene, note that this mix of emotions is entirely involuntary, and the jurors can often be unaware that they are feeling it—which makes it that much more effective.

After the study concluded, Salerno also suggested that the increasing ubiquity of cameras may mean that this factor will be an increasingly important one in jury trials to come. Personal cameras are cheaper, lighter, and used more frequently than ever; public and private surveillance cameras capture more everyday action than ever before, as well. That means that future prosecutors will be that much more likely to have visual evidence available to them when planning their cases.

“There are so many more opportunities for crimes to be captured on video, which means jurors are being exposed to really emotionally charged evidence,” Salerno said. “When judges weigh the informational value versus the prejudicial value of the evidence, it is important to be very mindful that the negative emotions roused by emotionally disturbing evidence can make jurors more likely to vote guilty.”

The multiple and simultaneous visual perspectives that play into the Lee Rigby murder trial will probably become more and more common. Even when dealing with cases much less heinous than that one, it’s probably worth keeping in mind the impact that this can have on juries. Judges should remain aware of the power of applied-moral-outrage when considering whether to admit visual evidence at trial.