How do we know whether judges of different backgrounds are "biased"? We review the substantial political science literature on judicial decision-making, paying close attention to how judges' demographics and ideology can influence or structure their decision-making. As the research shows, characteristics such as race, ethnicity, and gender can sometimes predict judicial decision-making in limited kinds of cases; however, the literature also suggests that these are by far less important in shaping or predicting outcomes than is ideology (or partisanship), which in turn correlates closely with gender, race, and ethnicity. This leads us to conclude that assuming judges of different backgrounds are biased because they rule differently is questionable: given that the application of the law rarely provides a ``correct'' answer, it is no surprise that judges' decisions vary according to their personal backgrounds and, more importantly, according to their ideology.
Do Justices telegraph their preferences during oral arguments? We demonstrate that Justices implicitly reveal their leanings during oral arguments, even before arguments and deliberations have concluded. Specifically, we extract the emotional content of over 3,000 hours of audio recordings spanning 30 years of oral arguments before the Court. Using only the level of emotional arousal in each of the Justices’ voices during these arguments, as measured by their vocal pitch, we are able to accurately predict many of their eventual votes, while using none of the text or substantive content. These predictions are statistically and practically significant and robust to including a range of controls. Our findings suggest that mannerisms that may be subconscious, such as vocal pitch, carry information that basic legal, political, and textual information do not, and can be used to predict the decisions of even elite political actors.