Study reveals vulnerability of Dutch criminal justice system to biases towards minority suspects

Heightened attention to immigration background led to biased decisions

The study, published as a working paper by the Institute of Labor Economics (IZA), documents how the media heavily linked Moroccan immigration background to criminal activity in the weeks following the 2019 murder of Derk Wiersum, a lawyer representing a key witness in a case against a criminal organization often referred to as the "Moroccan mafia". 

Using data from Statistics Netherlands, the researchers then compared criminal justice outcomes for Moroccan-Dutch suspects in the weeks just before and after this salience shock to those of individuals without any immigration background. This revealed that, while police and prosecutors did not alter their decisions, prison sentences imposed by judges increased by 79% for salient Dutch-Moroccan defendants who had nothing to do with the mafia killing.

Mitigating factors and broader socioeconomic consequences

Interestingly, the researchers noted that the impact of this bias was mitigated when cases were handled by more experienced judges in terms of interactions with minority defendants or years of practice. Despite this, the study found no corrective impact from appeals courts, suggesting that the initial bias in sentencing remained unchecked. Additionally, Moroccan-Dutch individuals affected by these biased decisions then experienced a 40% drop in labour income over the subsequent four years, underscoring the broader socioeconomic consequences of such judicial biases.

Training and guidelines could help mitigate similar biases

The findings from this study hint to potential measures to reduce judicial discretion in times of heightened public focus on minority-related crimes, suggesting that greater judge training and standardised sentencing guidelines could help mitigate similar biases in the future.