Research News

Supreme Court term limits could lead to constitutional whiplash: Study

Suzanna Sherry (Vanderbilt University)

A popular proposal to limit the term of Supreme Court justices to 18 years, with the most senior justice rotating off the court every two years, could introduce unprecedented instability into the constitutional doctrine on polarizing topics, according to two Vanderbilt law scholars.

Using computational methods rarely applied to legal research, Christopher Sundby, a student in Vanderbilt’s joint J.D.-Ph.D. program in law and neuroscience, and Suzanna Sherry, Herman O. Loewenstein Professor of Law, simulated the fate of a highly politicized decision—Roe v. Wade—under the 18-year plan.

They found that the ruling could have been overturned and reinstated up to three times in the past four decades as justices came and went.

“Presidents have gotten much better at choosing justices who align with their political beliefs,” explained Sundby, the lead author. “Pairing that with this term-limit plan could lead to more doctrinal instability than proponents have considered.”

They report their findings in Term Limits and Turmoil: Roe v. Wade’s Whiplash, forthcoming in the Texas Law Review.

The 18-year plan has been proposed by scholars to address concerns that the longevity of modern justices might leave them out of touch with the majority of today’s Americans. Proponents hope the plan would also make turnover on the Court so predictable and routine that it no longer becomes the political brawl it is today.

However, the researchers suspected that such a high degree of churn could have a considerable effect on the endurance of the Court’s decisions.

The researchers approached this question in a novel way: Mathematically. They used an algorithm called the Monte Carlo method, which enabled them to simulate multiple probabilities across multiple variables, to calculate the likelihood that Roe v. Wade would be overturned or reinstated in any given year from 1973 onward.

Their model took into account five variables. Two were historical: the party of the president and the composition of the Senate at the time of each justice’s nomination. Three were hypothetical: the degree of influence of the Senate, the loyalty of the justice to his or her nominating president’s ideology and his or her degree of deference to stare decisis, or legal precedent.

For example—would a justice appointed in 1985 by President Reagan and confirmed by a Republican-majority Senate with moderate influence decide to overturn Roe if that Justice was strongly influenced by stare decisis? The researchers calculated such a Justice would have a 70 percent probability of voting to overturn.

The researchers ran every permutation of these variables—10,000 calculations per justice per permutation—to determine the probability that the Court would choose to retain, overturn or reinstate the original decision.

They found that even low degrees of party loyalty could have resulted in the decision being overturned, reinstated and then overturned again over the subsequent four decades. Higher degrees of loyalty would simply have exacerbated those swings.

That level of instability could quickly become untenable, Sherry said, because stability is a cornerstone of American jurisprudence. “We don’t want the law to change every other week,” she said. “People need to know what the law is, not only so that they can act consistently with it but so that they can plan for the future. The predictability of the law is important for individuals, for businesses, for governments, for everybody.”

There was only one variable that could moderate those swings: deference to stare decisis.

A 10 percent degree of deference reduced the likelihood of a reversal from three times to one, and a 15 percent degree of deference brought that down to zero—enhancing stability but muting the very flexibility term limits are intended to encourage. Regardless, modern justices are simply not that deferential, the researchers noted—suggesting that we shouldn’t rely on that characteristic to insulate the Court from the dramatic reversals caused by political influence.

The researchers cautioned that their simulation was limited to a few variables and did not encompass every factor that might influence a justice’s decision. “I do think that it brings more power to the discussion, though, than simply hypothesizing,” Sherry said, “because it gives us a way to test our assumptions.”

Their findings suggest that they’re on the right track, Sundby said. “The fact that it was so consistent across so many different variable values and conditions suggests that these trends are reliable.”