¹ See, among others, J.A. Segal and A.D. Cover, ‘Ideological Values and the Votes of US Supreme Court Justices’, 83 American Political Science Review (1989) p. 557; L. Epstein and J. Knight, The Choices Justices Make (Congressional Quarterly Inc. 1998); J.A. Segal and H.J. Spaeth, The Supreme Court and the Attitudinal Model Revisited (Cambridge University Press 2002); L. Epstein et al., The Behavior of Federal Judges: A Theoretical and Empirical Study of Rational Choice (Harvard University Press 2013).

² See R. Gely and P.T. Spiller, ‘A Rational Choice Theory of Supreme Court Statutory Decisions with Applications to the State Farm and Grove City Cases’, 6 Journal of Law, Economics and Organization (1990) p. 263.

³ L.B. Tiede, ‘Mixed Judicial Selection and Constitutional Review’, 53 Comparative Political Studies (2020) p. 1092.

⁴ Ibid.

⁵ N. Garoupa et al., ‘Judging under Political Pressure: An Empirical Analysis of Constitutional Review Voting in the Spanish Constitutional Court’, 29 Journal of Law, Economics and Organization (2013) p. 513; N. Garoupa et al., ‘Loyalty to the Party or Loyalty to the Party Leader: Evidence from the Spanish Constitutional Court’, 67 International Review of Law and Economics (2021).

⁶ S. Amaral-Garcia et al., ‘Judicial Independence and Party Politics in the Kelsenian Constitutional Courts: The Case of Portugal’, 6 Journal of Empirical Legal Studies (2009) p. 381; S. Coroado et al., ‘Judicial Behavior under Austerity: An Empirical Analysis of Behavioral Changes in the Portuguese Constitutional Court, 2002-2016’, 5 Journal of Law and Courts (2018) p. 289.

⁷ L. dalla Pellegrina et al., ‘Litigating Federalism: An Empirical Decisions of the Belgian Constitutional Court’, 13 EuConst (2017) p. 305.

⁸ L. dalla Pellegrina and N. Garoupa, ‘Choosing between the Government and the Regions: An Empirical Analysis of the Italian Constitutional Court Decisions’, 52 European Journal of Political Research (2013) p. 558; N. Garoupa and V. Grembi, ‘Judicial Review and Political Partisanship: Moving from Consensual to Majority Democracy’, 43 International Review of Law and Economics (2015) p. 32, among others.

⁹ O.O. Varol et al., ‘An Empirical Analysis of Judicial Transformation in Turkey’, 65 American Journal of Comparative Law (2017) p. 187.

¹⁰ There is a distinction between writing disposition (measured by the individual decision to write and file a separate opinion) and writing skills (documented by textual analysis). Constitutional judges are typically assisted by legal clerks (in Spain, they are called letrados) in writing their opinions. This can impact writing styles, for example. However, unless one takes the view that there is a positive correlation between the support by legal clerks and judicial attributes (either legal background or appointing institutions), statistical results concerning writing dispositions are robust.

¹¹ See supra n. 5, among others.

¹² A good introduction to the Spanish Constitutional Court in English is provided by the following authors: I. Borrajo Iniesta, ‘Adjudicating in Divisions of Powers: The Experience of the Spanish Constitutional Court’, in A. Le Sueur (ed), Building the UK’s New Supreme Court: National and Comparative Perspectives (Oxford University Press 2004); L. Turano, ‘Spain: Quis Custodiet Ipsos Custodes?: The Struggle for Jurisdiction between the Tribunal Constitucional and the Tribunal Supremo’, 4 International Journal of Constitutional Law (2006) p. 151; V. Ferreres Comella, The Constitution of Spain (Hart Publishing 2013); E.C. Christiansen, ‘Forty Years from Fascism: Democratic Constitutionalism and the Spanish Model of National Transformation’, 20 Oregon Review of International Law (2018) p. 1.

¹³ The Constitution itself sets some conditions on constitutional judge eligibility: (i) background as career judge or prosecutor, law professor, civil servant or practising attorney; (ii) at least 15 years of professional experience; and (iii) renowned competence (whatever this may mean) for the position. In practice, with very few exceptions, Spanish constitutional judges have been either career judges or law professors since the Court was established in the early 1980s.

¹⁴ Ordinary courts may also raise challenges against the legislation they have to apply to a case pending before them (cuestiones de inconstitucionalidad). The political repercussions and motivations concerning these challenges are of a much smaller scale.

¹⁵ Órganos colegiados ejecutivos de las Comunidades Autónomas.

¹⁶ Asambleas de las Comunidades Autónomas.

¹⁷ Comunidades Autónomas.

¹⁸ For example, one career judge opted to practise law after his term at the Court (Mendizábal Allende). Still, we focus on backgrounds and not professional careers after terms at the Court.

¹⁹ J.O. Bercholc, ‘La Producción del Tribunal Constitucional Español a través del Ejercicio del Control de Constitucionalidad de los Actos Normativos de los Otros Poderes Políticos del Estado (1980-2011)’, PhD Dissertation (Faculty of Law, Universidad de Castilla-La Mancha 2016) (in Spanish).

²⁰ The classification of ‘centrists’ suggested by Jorge Bercholc, supra n. 19, is intrinsically subjective and debatable. However, we have not adjusted it to our own views about individual judges.

²¹ A more detailed list of individual classifications is shown on the supplementary materials, online.

²² Or only nine, if one were to exclude Encarnación Roca Trías, who for most of her career was a law professor. She joined the Spanish Supreme Court (a Court filled with career judges but having a quota for highly qualified jurists, most of whom are law professors) a few years before being appointed to the Constitutional Court.

²³ Concerning the constitutional judges appointed by the Judicial Council, their party identification is possible through the largely politicised judicial associations to which most judges nominated to the Constitutional Court belong. The major associations are Asociación Profesional de la Magistratura (conservative), Asociación Francisco de Vitoria (moderate), and Jueces para la Democracia (progressive).

²⁴ Concerning the composition of the Judicial Council itself, 12 of its members must be career judges in active service, and, for the other eight positions (the formal criteria for appointment is to be a jurist with excellent reputation and 15 years’ experience), career judges who are not in active service are eligible.

²⁵ One could even argue that, in the constitutional design, following the Italian experience, leaving a quota of appointments to the Judicial Council was the intended path of entry for career judges into the Constitutional Court, and a way to prevent the Court from becoming the exclusive domain of law professors.

²⁶ P. del Castillo Vera, ‘Notas para el Estudio del Comportamiento Judicial. El Caso del Tribunal Constitucional’, 20 Revista Española de Derecho Constitucional (1987) p. 177 (in Spanish).

²⁷ P.C. Magalhães, ‘Judicial Decision-Making in the Iberian Constitutional Courts: Policy Preferences and Institutional Constraints’, PhD Dissertation (Department of Political Science, Ohio State University 2002).

²⁸ C. Hanretty, ‘Dissent in Iberia: The Ideal Points of Justices on the Spanish and Portuguese Constitutional Court’, 51 European Journal of Political Research (2012) p. 671.

²⁹ See Garoupa et al. (2013), supra n. 5.

³⁰ See, among others, F. Ramos Romeu, ‘Law and Politics in the Application of EC Law: Spanish Courts and the ECJ, 1986-2000’, 43 Common Market Law Review (2006) p. 395; N. Garoupa et al., ‘Political Influence and Career Judges: An Empirical Analysis of Administrative Review by the Spanish Supreme Court’, 9 Journal of Empirical Legal Studies (2012) p. 795; J.A. Mayoral Díaz-Asensio, ‘La Politización de la Aplicación Judicial del Derecho Europeo: Un Estudio del Tribunal Supremo Español’, 161 Revista de Estudios Políticos (2013) p. 117 (in Spanish).

³¹ J. López-Laborda et al., ‘Is the Spanish Constitutional Court an Instrument of the Central Government Against the Autonomous Communities?’, 29 Constitutional Political Economy (2018) p. 317; J. López-Laborda et al., ‘Consensus and Dissent in the Resolution of Conflicts of Competence by the Spanish Constitutional Court: The Role of Federalism and Ideology’, 48 European Journal of Law and Economics (2019) p. 305.

³² See Garoupa et al. (2021), supra n. 5.

³³ See supra n. 5.

³⁴ See Garoupa et al. (2013), supra n. 5.

³⁵ See Tiede, supra n. 3.

³⁶ A few law professors were also practising lawyers, either before or after their terms in the Court (Diez-Picazo, García-Pelayo, Garrido Falla, Gimeno Sendra, Gómez-Ferrer, Jiménez de Parga, Menéndez Menéndez).

³⁷ We do not have general and systematic data about the proportion of law professors who have practised law during a relevant part of their careers, and we are not aware that such data are available. However, the fraction of practising law professors is generally considered relevant in Spain, although perhaps decreasingly so in recent decades. There seems to be a large variance across legal fields. For instance, professors of private law are typically more likely to be engaged in private practice than professors of constitutional law, legal history, or legal theory. Among law professors who sat at the Constitutional Court, a significant number (around 15) did practise law in a relevant way either before or after their term in the Court.

³⁸ Several career judges did this after retiring from the bench (Conde Martín de Hijas, García Manzano, Mendizábal Allende, Rodríguez Arribas and Sala Sánchez) but had not been engaged in private law practice before.

³⁹ These differences can be mitigated by access to legal clerks in the Court.

⁴⁰ We use STATA 15.

⁴¹ See Tiede (2020), supra n. 3.