New research finds color photos of bloody scenes elicit disgust, which colors jurors’ decisions.

By Tom Jacobs

(Photo: Kristian Karlsson/Unsplash)

Some of the most important decisions trial court judges make involve admissibility of evidence. A crime-scene photograph can provide jurors with useful information — or evoke a visceral reaction that biases them in favor of conviction.

It’s a consequential call — and, in many cases, a tricky one to make. Newly published research points to a simple way of providing vital visual information without prejudicing the jury: Provide them only black-and-white images.

In a mock-juror study involving a murder case, “color gruesome photographs increased convictions via the disgust they elicited,” writes psychologist Jessica Salerno of Arizona State University. This effect was eliminated when the same photographs were presented in black and white, she reports in the journal Psychology, Public Policy, and Law.

Salerno conducted two studies in which mock jurors recruited online (193 in the first, 354 in the second) were presented with evidence from a real-life trial in which a man was accused of murdering his wife. The participants — all American citizens — all saw emotionally neutral photographs of the crime scene.

Some additionally saw grisly images, including one that showed the victim’s face and upper body covered in blood. These participants were randomly assigned to see the photos in either black-and-white or color.

After viewing all the evidence (a 20-minute procedure), the mock jurors voted guilty or not guilty, and noted their level of anger and disgust.

“Color gruesome photographs consistently made jurors feel more disgusted than if they only read detailed verbal descriptions of the injuries,” Salerno reports. These uncomfortable feelings “in turn made them more likely to vote guilty.”

“This was consistently not the case when the same gruesome photographs were presented in less vivid black-and-white,” she writes. “Despite the color and black-and-white gruesome photographs conveying the same probative information, they only increased disgust and, in turn, convictions when they were presented in color.”

In both studies, this effect “was stronger among mock jurors who tend to be relatively more aware of the psychological occurrences in their body,” she adds. This suggests the color images evoked visceral emotions that made jurors physically uncomfortable, increasing their predilection to vote guilty.

The results “provide preliminary support for a relatively easy intervention,” Salerno concludes. Indeed, while larger studies will be needed to confirm these results, sticking to black-and-white images where blood is involved could be an important element in ensuring a fair trial.