Does Jury Size Affect the Outcome of a Trial?

In our lesson this week, we learned that jury size can affect the outcome of the trial. Mathematicians have been working to try to determine if different jury sizes really can have an impact on the conviction of the defendant. One mathematician, Jeff Suzuki, did a lot of research regarding this topic. However, he used a hypothetical defendant, not a real example. In the past, mathematicians believed that each the probability of making the correct decision regarding the defendant was the same for each juror. For Suzuki’s research, he used three probabilities to calculate his data. This included the probability of the defendant actually being guilty, the probability of a juror making the right decision if the defendant was guilty, and the probability of the juror making the right decision if the defendant is innocent. From the research, Suzuki gathered that all juries, regardless of size, are likely to declare the defendant guilty when “the evidence suggests that a defendant is most certainly guilty” (Gorski, 2016). However, he also found that when it appears to be less certain that the defendant is guilty, it is more likely for a smaller jury to convict the defendant than a larger jury. It is important to keep in mind that this research and data does not take everything into consideration, like juror interaction, evidence, etc.

I found this information to be very interesting, even though it was just based off of a hypothetical situation, because it corresponds with what we learned in our lesson this week. We learned that a smaller jury is more likely to convict someone than a larger jury. This is because when the jury consists of six people, rather than twelve, it is more likely for someone who disagrees to conform to the incorrect decision that the rest of the jury agrees on. In a 12 person jury, there is a higher likelihood that more than one person will disagree with the rest. And since there are two of them, rather than one, it is more likely that they will be confident in their opinion and not conform with the rest. With that being said, it is much more fair to have a jury of 12 rather than 6.


Gorski, C. (2016, July 22). The Mathematics of Jury Size. Retrieved from

1 comment

  1. Alexandra Kalasky

    I never really understood why any case would have a small jury due to the fact that their verdict impacts the defendant’s life. There is too much on the line to have just a handful of people deciding whether someone is guilty or not. I believe a larger jury size gives more perspective and reasoning to decision-making that results in more incisive verdicts. Smaller jury sizes increase the chances of unanimity, but it was found that larger juries are more likely to correctly convict given cases (Luppi & Parisi, 2013). This study by Barbara Luppi and Francesco Parisi (2013) analyzed different jury sizes and how it affects judgment and convictions and concluded that although there is more input and opinions in larger juries, they reached the correct ruling compared to smaller juries. This is an important find that should be taken into consideration when selecting a jury and deciding what size is appropriate.

    Luppi, B., & Parisi, F. (2013). Jury Size and the Hung-Jury Paradox. The Journal of Legal Studies, 42(2), 399-422. doi:10.1086/670692

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