PhD Defence Jerôme Lam | All in Search of the Missing - Citizen and Police Participation in Missing Person Searches

All in Search of the Missing - Citizen and Police Participation in Missing Person Searches

Jerôme Lam is a PhD student in the Department of Psychology of Conflict, Risk and Safety. (Co)Promotors are prof.dr. J.H. Kerstholt from the Faculty of Behavioural, Management and Social Sciences and dr. N. Kop from the Police Academy.

In the Netherlands, approximately 30,000 people are reported missing to the police each year. In some of these cases, large-scale search operations are initiated by citizens. Such citizen-led searches present both opportunities and risks. On the one hand, citizens can act as valuable additional “eyes and ears,” enabling the search to cover a larger area. On the other hand, these actions can disrupt official investigations, for example by destroying traces or evidence, or by creating a lack of coordination and oversight. However, the police often have limited formal authority to prevent or direct these citizen search efforts.

The aim of this dissertation is to gain a deeper understanding of how and why citizens participate in searches for missing persons. It explores how citizens and police collaborate, what psychological factors motivate citizens to take part in search efforts, why investigators choose to involve citizens, and how technology can support these volunteers during searches.

The dissertation consists of five studies. The first is a case study examining collaboration between citizens and police during an actual missing person investigation. Subsequently, two survey studies examined the factors underlying citizens’ intentions to participate in search efforts, considering both the characteristics of the missing person cases and the cognitive and affective drivers of potential volunteers. A third survey study investigates investigators’ intentions to involve citizens, through the lens of the Theory of Planned Behavior. The final study uses a quasi-experimental design to examine the impact of a specially developed mobile application on a citizen-organized search.

Overall, the dissertation demonstrates that citizen participation in missing person searches is not static but dynamic, shaped by contextual, cognitive, and affective factors. It also highlights both the potential benefits and the limitations of technological tools designed to support citizen search efforts.