Cite your sources! Misinformed juries deliver biased verdicts

Imagine you are one of the jurors tasked with the responsibility of determining guilt in a murder trial. The trial is long, and you are given a plethora of information every day to remember about the case. How confident are you that you could remember everything that happens throughout the trial accurately? If you misremember something, does that compromise the integrity of your decision as a juror? More importantly, how can you know for sure if you’ve remembered everything correctly?


Although jurors are instructed to reach a verdict based solely on the evidence presented to them at trial, if a juror misremembers something from the trial and passes that to other jurors, could it affect the final verdict of the jury? In “Misinformation encountered during a simulated jury deliberation can distort jurors’ memory of a trial and bias their verdicts”, Thorley and colleagues (2020) examined how erroneous details brought forth by other jurors can affect jurors’ memory of and decisions about a criminal trial.


In the study, jurors watched footage of a real murder trial, and read a transcript of the jury deliberation. Within this transcript, some participants received 6 additional statements conveying pro-prosecution misinformation – information that was not in the original trial but was presented as if it had been. Half of the jurors were allowed to take notes during the trial, while the other half were not. After deliberation, participants were asked about their memory of different evidence and where they learned the information (i.e., a source monitoring test) to test whether jurors were misremembering where they learned information.


Results from this study indicated that participants presented with misinformation about the trial believed, on average, that 31% of the pro-prosecution misinformation actually appeared in the trial – their memories had changed to adopt the misinformation into their memory of the trial. In addition to this, jurors who misremembered the most information – those who adopted the most amount of misinformation into their memories – were also the most likely to render a guilty verdict. Allowing jurors to take notes (presumably so they could have mor information about what actually happened during the trial) did not change these effects. Therefore, jurors are just as likely to misremember the information brought in during deliberations as occurring as part of the trial even if they have their own record of what was said during trial.


In real trials, jury deliberations are private. We do not know what is going on behind closed doors of the jury room, except in very rare circumstances. Thus, it is virtually impossible to know how much misinformation is being spread and used during deliberations and how it impacts verdicts. Thorley and colleagues have given us a glimpse into the negative consequences of misinformation in a jury. Going forward, it’s important to find ways to minimize and measure the amount of misinformation that can spread throughout a jury.


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