- Published: November 5, 2012
There is an old saying that tells us that a picture is worth a thousand words. While this can help us keep some of fondest moments in memory, the idea has no place in a court of law. When looking at the mind of a juror, one must pay careful attention to possible biases or predispositions. Unfortunately, neuroimaging itself poses such a threat. Some studies have suggested that “introducing neuroimages into the courtroom could perhaps do more damage than good” (Nadelhoffer, 2009).
Federal Rules of Evidence 403 states that evidence can be excluded “if its probative value is substantially outweighed by the danger of unfair prejudice” (Nadelhoffer, 2009). Essentially, if a piece of evidence would be unfairly influential, it must be barred from a court. One study examined conviction rates with and without pictures (Nadelhoffer, 2009). Some participants were shown anything from none, to neutral, to graphic photographs (Bright & Goodman-Delahunty, 2006). The conviction rates were more than 5x higher when pictures were included, even though they did not add any relevant information (Bright & Goodman-Delahunty, 2006). Although the images presented were not neuroimages, the study still has implications for the power of the visual.
Another study that examined the power of visuals was even more disturbing. Participants were presented with bad arguments such as “watching TV helps with math ability because both activate the temporal lobe” (McCabe & Castel, 2008). Some participants were also given bar graphs or images to accompany the text (McCabe & Castel, 2008). Those who received brain images to support the written information were more likely to conclude that the bad arguments made sense (McCabe & Castel, 2008). This rate was also higher when compared to participants who received bar graphs; in other words, the type of visual data (brain imaging) had an additional impact (McCabe & Castel, 2008).
Neuroscience is certainly an extremely promising field, but we do need to be careful how much weight we give to its findings. At present, the technology we have only has limited certainty. Unfortunately, even if the data is only meant to be a piece of a court-case puzzle, studies such as the ones above show that they may be dangerously powerful and influential. As a species, we love pictures; we think they have all the proof and answers we would ever need. We just have to be careful not to attribute to them omnipotence.
Bright, D.A. & J. Goodman-Delahunty. 2006. Gruesome evidence and emotion: Anger, blame, and jury decision-making. Law and Human Behavior 30: 183-202.
McCabe, D.P. & A.D. Castel. 2008. Seeing is believing: The effect of brain images on judgments of scientific reasoning. Cognition 107: 343-352.
Nadelhoffer, T. (2009, March 10). Jurors, brain imaging, and the allure of pretty pictures. Retrieved from http://thesituationist.wordpress.com/2009/03/10/jurors-brain-imaging-and-the-allure-of-pretty-pictures/