כיצד בוחרים שופטי בית המשפט העליון את חבריהם להרכב

Until recently, a procedure in the Supreme Court of Israel allowed each justice to compose three-justice panels. This unique ability of justices to compose panels allows us to test three theories of panel composition by justices: random selection, professional selection, and strategic selection. We assembled an original database of decisions made under this procedure during a two-year period in which the composition of the court remained stable (around 800 court decisions, from January 2015 to April 2017). The data reveal a strong bias in justices’ panel composition. A Gini coefficient measuring the extent of inequality in each justice’s panel composition, which ranges from 0 (total equality) to 1 (total inequality), is 0.82 on average, which contradicts the random composition theory. The high variance in the choice of panel members contradicts the professional composition theory. The data support the idea that justices compose panels strategically, and this theory is also supported by several case studies. Accordingly, the data uncover justices’ revealed preferences for panel members. We use the data to depict relationships within the Supreme Court of Israel, and identify three groups of justices. We also show that justices who were selected by the current Chief Justice under the above procedure before she became Chief Justice are more likely to sit on a panel with her in ordinary hearings after she became Chief Justice. Since the Chief Justice has the legal authority to compose ordinary panels, this is also consistent with strategic panel composition. In light of our findings, we conclude by recommending a change in the manner in which panels are composed on the Supreme Court of Israel. We recommend the use of computer software to compose all judicial panels randomly, and to determine the identity of the justice on duty who deals with each petition.