Keys to Detention: Lessons from research

Published on 09 October 2026

What do we know about detention, and what can that tell us about punishment, security, reintegration into society, and immigration detention in the Netherlands?

In the book Sleutels tot detentie – Lessen uit de wetenschap (Keys to Detention: Lessons from Research), researchers on the Criminal Justice research programme at the Institute of Criminal Law and Criminology combine key insights from years of legal and criminological research on detention.

The Dutch prison system is under significant strain. It faces staff shortages and capacity problems, while fundamental questions persist about the effectiveness of prison sentences, conditions in detention, and the reintegration of detainees into society.

45 practical lessons for reintegration professionals  

According to the researchers, it is especially important when considering these questions that scientific knowledge should play a central role. In Sleutels tot detentie, they have taken existing legal and criminological research and translated it into 45 practical lessons for the legislature, the judiciary and the Public Prosecution Service, the Ministry of Justice and Security, the Netherlands Custodial Institutions Agency, and organisations involved in the reintegration process.

With these 45 accessible lessons, the authors show how detention works in practice, the impact it has on prisoners, staff and society, and the dilemmas behind political and public debates on punishment and security. Current challenges within the prison system are connected to empirical research, legal principles and insights from practice. By sharing the outcomes of research with policymakers and the wider public, the book aims to contribute to a considered, realistic and better-informed debate about the future of detention in the Netherlands.

Among other recommendations, the authors call for a more restrained use of pre-trial detention, using community service as a form of punishment instead of short prison terms, a long-term approach to prison capacity planning, and improved healthcare in detention. The book also offers lessons on visitation arrangements, fatherhood in detention, forensic care, immigration detention, housing and debt after release, and reducing reliance on Certificates of Conduct (VOGs).

Book launch in the Koepelgevangenis 

The book launch of Sleutels tot detentie was held on Friday 9 October in the Koepel, a former panopticon-style prison in Haarlem. The authors presented a selection of their lessons, while representatives from the judiciary, the prison service, probation services and people with lived experience reflected on the implications of these lessons for policy and practice.

At the event, the first copy of the book was presented to Claudia van Bruggen, Minister for Legal Protection and Prisons. Jessica Westerik (board member of Dutch Probation Service), Jacco Janssen (senior judge at the District Court of Rotterdam), Piet Broenland (coordinator for lived-experience expertise at the Salvation Army Probation Service), and Toon Molleman (Director of Prisons and Immigration Detention at the Custodial Institutions Agency (DJI)) shared their reflections on the book.

Publication 9 October | 344 pages | isbn 978946164 6811 | price € 22.50 

Editors: Miranda Boone, Paul Nieuwbeerta, Elina van ’t Zand, Jeroen ten Voorde, Risha Jagarnathsingh 

Sleutels tot detentie - Lessen uit de wetenschap - Uitgeverij Van Gennep 

Institute of Criminal Law and Criminology - Leiden University

If you would like to receive a PDF of the book (in Dutch) for media purposes, send an email to Risha Jagarnathsingh ([e-mail]) or Chris ten Kate ([e-mail]).