The Necessity of Nine

By Thomas Cribbins

Thomas Cribbins is a student at the University of Michigan studying political science.

While we currently sit with eight members on the Court, there have been calls by scholars and politicians to reduce the size of the Court in order to reduce judicial activism and force more compromise on the Court. The number often repeated is six: the original number of the court. [1] However, having nine Justices is very beneficial, and the Condorcet Jury Theorem proves that nine is better than six.

The Condorcet Jury Theorem is a model that demonstrates the fact that groups are better decision-makers than individuals. This applies nicely to the U.S. Supreme Court because the limitations to this model apply neatly to the Supreme Court as we normally know it. First, there should be an odd number of Justices in order to prevent ties. Second, each justice should “get it right” more than 50 percent of the time. Finally, a majority vote to affirm or reverse will control the decision of the Court. [2] These three assumptions are entirely reasonable for the normally functioning Court. Most likely, the most contestable of the assumptions as they relate to the justices would be the ideological argument that certain justices do not have better than a 50 percent accuracy, but that notion comes from a deeply stubborn point of view that disparages any value in a Harvard or Yale law degree. The Supreme Court has nearly undeniably made a few mistakes; Buck v. Bell (1927), Korematsu v. U.S. (1944), Dred Scott v. Sanford (1857), Plessy v. Ferguson (1896), but the fact that these few form the majority of the indisputable mistakes demonstrates that the Supreme Court rarely makes an incorrect decision. Besides, the point being that a smaller court would simply allow for more mistakes to be made.

The Condorcet Jury Theorem is quite intuitive. For example, fewer justices equals more mistakes. However, the model proves that nine is better than six or a lower odd number. While the accuracy of the justices is highly contestable, if we presume that all the justices are about 65 percent accurate, then a five member court would have a 76.5 percent chance of choosing the correct decision. If we hold the individual juror accuracy constant and simply add 2 more justices, then the accuracy of the Court goes up to 80 percent. And if we get to nine justices, the accuracy goes up to 82.8 percent. [3] While these differences may seem like only a few percent, that small difference can be hugely consequential.
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Consider for a moment, if a habeas corpus case rose all the way to the Supreme Court of the United States, as many do throughout the year. We can infer that this case will have serious implications for the country in whatever facet of criminal law it contends. This case should have the best shot at being decided correctly. This prisoner has already faced incredible odds and almost certainly suffered a wrongful detention if their case is so murky the Supreme Court decides it is valuable time spent. We, as a society, would want the rule of law to prevail every time in this case. If a Court of six justices upholds your conviction there is no recourse. Salvation squashed. But what if we just added a few more justices with similar credentials? This case has gotten a second chance at fairness, probably at least a 6 or 7 percent better chance.

If there is mathematical proof that nine justices better adjudicate cases than six, seven or eight, than why should we ignore a better chance at justice? Don’t we owe everyone the best chance at a fair legal system? While the Condorcet Jury Theorem cannot capture all the intricacies of the structure of the Court, it provides a powerful demonstration that nine justices are better than six. While this model glosses over nuances like voting coalitions, recusals or ties at the Court, it still shows that it is far more probable that the Court still picks the correct decision than the wrong decision. And the statistics above are still predicated on the assumption that the average justice is only 65 percent accurate, which is a gross understatement, but still shows how accurate a nine member Court will be even with an unrealistic lack of skill.

In short, despite the critics, we need a nine member Supreme Court. Beyond all the partisan politics, it can be empirically proven that nine is better than six or seven or eight. And we owe it to the nation to deliver justice as expertly and often as possible.

[1] Albert, Richard. "No Need for Nine on the Supreme Court - The Boston Globe." BostonGlobe.com. February 22, 2016. Accessed October 24, 2016. https://www.bostonglobe.com/opinion/2016/02/22/need-for-nine-supreme-court/7SnAzJWXMveAxlTzOsDWzM/story.html.
[2] Page, Scott, and Lu Hong. "Re-Interpreting The Condorcet Jury Theorem." October 5, 2015. Accessed October 24, 2016. http://www.law.nyu.edu/sites/default/files/upload_documents/Re-Interpreting the Condorcet Jury Theorem.pdf.
[3] Page, Scott. Condorcet Jury Theorem.
Photo Credit: Brain Turner
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