Legal Psychologists as Experts

In the research project Legal Psychologists as Experts, we examine whether legal psychologists who frequently write expert witness reports in criminal cases may be vulnerable to bias. The project is funded by a NWO Open Competition M grant awarded to prof. dr. Annelies Vredeveldt. The project is led by PhD candidate Eva van Rosmalen, supervised by Annelies Vredeveldt, Jan de Keijser and Tanja van Veldhuizen.

In their expert witness reports, legal psychologists address questions from judges, prosecutors and lawyers about the validity of statement evidence – for example, whether there are indications that a confession may be false. This type of expert testimony can be especially crucial in cases that often lack supporting evidence, such as sexual assault cases.  However, when experts get it wrong, their work can contribute to serious miscarriages of justice.

Extensive research in other expert fields – such as forensic science and forensic psychology – has shown that experts are not immune to cognitive biases. Legal psychologists are often quick to point out bias in others, for instance when pointing out confirmation bias in police investigations. Since biases are fundamentally ingrained in human thinking processes, the question arises whether legal psychologists themselves are also vulnerable to biases.

In this research project, we aim to 1) provide insights into the quality of legal psychological analyses, based on real-world expert witness reports, 2) strengthen the empirical evidence base on cognitive biases in legal psychological expert witness reports, 3) provide a comprehensive overview of the evidence base and gaps in knowledge and 4) formulate evidence-based policy recommendations for legal psychologists serving as expert witnesses, as well as other practitioners who deal with expert witness reports.

In four subprojects, we will 1) examine the quality of real expert witness reports written by Dutch legal psychologists, 2) analyse cases in which two or more legal psychologists have written a report and came to conflicting conclusions, 3) conduct four experiments to assess whether legal psychologists are susceptible to bias when writing their expert witness reports and whether certain strategies can mitigate these biases.

Earlier work on this topic includes an article on best practices for writing expert witness reports, published in the Dutch professional journal Expertise & Recht (Expertise & Law), which has since been translated into English. It also includes a review on bias in legal psychological assessments, published open-access in Psychology, Crime & Law, in which we outline several practical recommendations for minimizing bias when writing expert witness reports.