Legal Ambiguity and Judicial Bias: Evidence from Electoral Corruption Trials in 19th-Century Britain

Abstract

In legal systems where partisan (or otherwise partial) judges issue biased rulings, reformers generally focus on making judges less partial. We highlight an alternative approach to controlling bias: reducing legal ambiguity and thus constraining partisan judges’ ability to make biased decisions. We develop a model of partisan justice that shows how biased rulings depend on both legal ambiguity and judges’ preferences. We then provide evidence that an increase in legal clarity reduced the partisan bias of electoral corruption trials in 19th-century Britain — a setting in which bias can be credibly measured both before and after separate reforms that affected legal ambiguity and (for comparison) judicial independence. Historians have argued that making these trials less partisan helped combat electoral corruption, but while they have focused on the role of judicial independence in accomplishing this, we show that making law less ambiguous played at least as large a role.