Does heightened media attention to minority groups influence judicial decision-making? Our research (joint with Nadine Ketel from Vrije Universiteit Amsterdam) examines how a sudden increase in public attention to individuals of Moroccan descent in the Netherlands affected criminal sentencing. Using high-quality administrative data, we find that while police and prosecutors did not alter their behaviour, judges imposed prison sentences that were 72% longer for affected defendants. This effect was observed only on sentencing length, the decision with the most judicial discretion, and was mitigated by more experienced judges. These biased judgements were not corrected in appeals court, raising concerns about judicial checks and balances.
Cognitive biases can shape judicial decisions, particularly when decision-makers rely on practical methods under pressure. Psychological research shows that salience – how much a particular feature stands out – can influence choices, sometimes reinforcing stereotypes. In the criminal justice system, this can lead to bias when external events heighten the visibility of certain groups. We investigate such a case following the 2019 assassination of Dutch lawyer Derk Wiersum, who represented a key witness in a major trial against a criminal network linked to Moroccan-Dutch individuals. The extensive media coverage that followed intensified the public perception of Moroccan identity in a criminal context, providing an opportunity to examine whether this influenced judicial outcomes.
Studying bias in sentencing
We analyse comprehensive data on the Dutch criminal justice system, tracking cases from arrest to appeal. To isolate the effect of the salience shock, we compare sentencing outcomes for Moroccan-descent defendants before and after the event to those of defendants with no migration background, called a difference-in-differences approach. Crucially, our identification strategy focuses on suspects of Moroccan descent who had no ties to the criminal organisation at the centre of media attention, and who committed their offense (long) before the shock. This implies that observed differences are driven by bias and not by changes in the number or type of offenses committed. Our findings reveal a clear pattern: while police and prosecutors' decisions remained unchanged, judges significantly increased the prison sentences for Moroccan-descent defendants by 72%.
Notably, this effect was confined to sentencing length, which allows for the most judicial discretion and is consequently the most susceptible to subjective judgement and implicit bias. Moreover, the effect was strongest in courts where judges had less prior experience with Moroccan defendants. At the same time, we find no evidence of spillover effects to other minority groups, showing that judges rather specifically targeted the treated group.
‘Our findings emphasise the need for safeguards against bias in judicial decision-making, especially when external events heighten attention on specific groups’
Revisiting the long-term consequences
A critical aspect of our study is that judicial checks and balances failed to correct this bias. Despite the availability of appeals, harsher sentences imposed after the salience shock were not reversed by higher courts, highlighting a key weakness in the judicial system’s ability to self-correct. While clear legal mistakes in sentencing may be identified and corrected on appeal, variations in sentence length – especially when they occur systematically across multiple cases – are less likely to be overturned. This appears to be what happened after the salience increase, something unlikely to be spotted and corrected by the system.
Beyond sentencing, we examine potential long-term effects. While not statistically significant, our estimates suggest a negative trend in employment and earnings, consistent with broader research on discrimination.
Implications for justice and policy
Our findings emphasise the need for safeguards against bias in judicial decision-making, especially when external events heighten attention on specific groups. One possible intervention is to increase training to reduce the reliance on cognitive shortcuts, particularly for less experienced judges. Additionally, strengthening the transparency and review mechanisms in sentencing could help reduce differences between sentences. More broadly, our study underscores that the criminal justice system does not operate in isolation, public narratives and media coverage can influence judicial behaviour in ways that reinforce systemic inequalities.
Addressing these issues requires a multi-pronged approach that includes policy reforms, public awareness campaigns, and continued research into the mechanisms driving judicial bias. By fostering a greater understanding of how external influences shape courtroom decisions, we can work toward a legal system that better upholds principles of fairness and impartiality.
About Olivier Marie
Olivier Marie is Professor of Labour Economics at Erasmus School of Economics. He is interested in studying crime, education, and discrimination from an economic angle.
About Kyra Hanemaaijer
Kyra Hanemaaijer, a recent PhD graduate from Erasmus School of Economics, is now a postdoctoral researcher at the University of Gothenburg, focusing on crime, education, and gender economics.
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