Through the course of a single term, the Supreme Court went from a “boring” eight member body to one apparently itching to take on polarizing political issues.  This transformation took place in the Court’s first full term without Justice Scalia since 1986.  Some (including Justice Breyer) speculated that Scalia’s absence would have a large impact on the Court.  Others see Gorsuch as a jurisprudential successor to Justice Scalia as well as the justice filling his seat.  How did the justices react to Scalia’s absence? This post looks at the development of Supreme Court precedent through the justices’ citations in the 2016 term.

To do this there are a few points to note about the data in this post.  First, signed majority opinions are the only analyzed units.  Second, duplicate cites within the same case are only counted once.  Third, only cites to Supreme Court cases are counted.  This means that cites from this term’s separate opinions (concurrences or dissents), multiple cites to the same source in a case, and cites to lower court cases are not accounted for in this post.  These restrictions allow for a focus on the development of Supreme Court precedent and for an analysis of citation relationships among the justices.

While the Court had its lowest majority opinion output in modern history, there was substantial variation in the number of unique citations per case.  Below are the majority opinions with the most unique citations per the metric used in this post.

Justice Kennedy’s majority opinion in Ziglar cited the most unique cases by far with 61. The case with the next most unique cites, Justice Alito’s opinion in Matal v. Tam, has fifteen fewer cites with 46.  After Morales-Santana with 40 there is another significant dip to Justice Kennedy’s opinion in Pena-Rodriguez with 28.

Perhaps not surprisingly based on this metric, Justice Kennedy was the most cited of all justices this term.

Justice Scalia was the second most frequently cited justice this term with 61 cites to his opinions.  He was also the most cited non-sitting justice and was cited more than all other sitting justice aside from Justice Kennedy.  The sitting justice cited the most frequently after Justice Scalia was Justice Ginsburg with 43 cites to her opinions.  Justice Kagan was the least cited of the justices in this figure with 12 citations to her decisions.  Since the cut point for this figure is 12 citations Justice Sotomayor is not shown.

When only looking at sitting justices cited in Supreme Court opinions we get the following figure

Justice Sotomayor was cited to the fewest number of times of all sitting justices this term with ten cites to her opinions.  After Justice Kagan, there is a large jump in number of cites to Justice Alito’s decisions. Justice Alito though also sat on the Court for five more years than Justice Kagan and this plays into the number of times his decisions were cited.

We can visualize this a bit differently adjusting for time.  Since justices with more time on the Court have more opportunities to write opinions, the following figure which examines whether and to what extent justices with longer tenure on the Court are cited more frequently shows greater parity among justices.  This figure looks at the justices’ cite counts divided by years that they sat on the Court.

While Justice Kennedy is still the top cited sitting Justice, Justice Roberts and Alito are close behind.  Justice Thomas is actually the least cited justice based on his number of years on the Court.

The citations this term were to a variety of cases with some recent and many historic. To see how the citations spread across time the following figure shows the counts on a yearly basis.

There is a decreasing number of citations from cases decided in 2014 to cases decided in the current year as the justices have had little time to filter the most modern cases into streams of precedent.  The decision year with the most citations is 1991.  Interestingly, no citation from 1991 came up in more than two majority opinions.

By contrast multiple cases were cited in three or more opinions across this term.

The decision cited most was Justice Ginsburg’s decision in Cutter v. Wilkinson  – specifically for the sentence in footnote 7, “we are a court of review, not of first view.”  Other decisions cited in multiple opinions include Justice Black’s 1946 decision in Bell v. Hood and Justice Rehnquist’s 1979 decision in Bell v. Wolfish.  The oldest case in this figure is Justice Field’s often cited 1877 decision in Pennoyer v. Neff.  The most recent is Justice Alito’s decision from last term in Spokeo v. Robins.

As may be apparent, all cases are not cited equally and all justices do not cite equally.  Some sitting justices average a higher number of citations per case than others.  We can see this with the justices’ total number of citations from their majority opinions this term.

Justice Kennedy cited to over 60 cases more than the justice with the next most citations, Justice Ginsburg.  Justice Gorsuch cited to six Supreme Court decisions in his majority opinion in Henson v. Santander.  When these citation counts are divided by the number of majority opinions the justices wrote this past term, Justice Kennedy still retains the top spot although the disparity between him and the rest of the justices is not as great.

The number of citations in the above figures is not only from other justices but also from the authoring justices themselves.  The justices with the most outward and inward citations also tend to cite themselves frequently.

Justices Kennedy and Ginsburg cite themselves the most, while Justice Sotomayor, the least cited of the sitting justices also cites herself the least.  Does Justice Kennedy cite himself more than he cites any other Justice? The answer is shown in the following figure looking at the most frequent pairs of citing/cited justices.

Justice Kennedy did in fact cite himself more than any other justice and this is the highest cite pair count across all justices for the term.  Justice Kennedy’s cite relationships also place him in the second and third position for cite pairs based on his citations to Justice O’Connor’s and Justice White’s decision.  Sometimes these cite pairs are somewhat unexpected as may be the case with Justice Roberts citing to Justice Stevens.  Justice Roberts cites to a variety of Justice Stevens’ decisions including twice to the decision in Williams v. Taylor. 

As this post shows the Justices cite each other and themselves in expected and unexpected ways.  There are patterns to the Court’s development of its jurisprudence and commonalities based on those who cite frequently and those who cite less frequently.  These citations are also a factor of the types of cases the justices hear as well as the case complexities.

In the year after Justice Scalia’s final year on the Court it is well worth paying attention to the justices’ citations to his decisions.  On this note three justices – Justices Kagan, Breyer, and Alito cited Justice Scalia’s opinions more than those from any other justice including themselves.  The lasting quality of Justice Scalia’s opinions, while discernible this term, will become more or less apparent as they are cited in cases in upcoming Supreme Court terms.

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