Dutch Suspects of Terrorist Activity: A Study of Their Biographical Backgrounds Based on Primary Sources.


  • Maarten van Leyenhorst Analyst and Trainer at the Dutch Institute of Forensic Psychiatry & Psychology in The Netherlands
  • Ada Andreas Policy Advisor to the Dutch Probation Service


Salafi-Jihadi Terrorism, Primary Source, Early Warning Signs, Reintegration, Probation Services


With the impending defeat of ISIS in Syria and Iraq, supporters of terrorist groups, among them home-grown supporters and returning foreign fighters, have become a huge security threat to their country of return. Some have committed attacks in western countries, even while under the surveillance of authorities. Counter-terrorism is confronted with enormous challenges. One of the most prominent issues is the absence of evidence based knowledge on early warning signs. Experts on radicalization and terrorism have emphasized that neither typologies of terrorists nor accurate descriptions of generalizable risks can be made. This leads to opportunities for those who are willing to prepare and commit acts of terrorism to do so, without the agencies in charge of monitoring such individuals being able to accurately identify relevant threats. An additional deficiency in counter-terrorism research, is its dependency on historic and secondary source material. One of various actors in the Netherlands tasked to evaluate and mitigate relevant risks of terrorist suspects and offenders, is the Dutch Probation Service (DPS). In response to today’s prevailing terrorist threat, a specialized section of the DPS is set up to identify and supervise potential problem behaviour of those who are suspected or convicted of terrorism. The authors have been involved in this Unit Terrorism, Extremism and Radicalization (TER) for years. As professionals of TER, the authors have had unique access to both judicial data, such as police files and prosecutor’s data, as to experts in the Dutch field of counter-terrorism. The authors have analysed the pre-sentencing advices of twenty-six clients of the DPS. These files are comprised of several socio-economic, historical, psychopathological and behavioural indicators. The goals are to learn from the analysis of the biographical backgrounds of the suspects and to stimulate the debate on management and supervision of terrorist offenders. 

Author Biography

Maarten van Leyenhorst, Analyst and Trainer at the Dutch Institute of Forensic Psychiatry & Psychology in The Netherlands

m.v.leyenhorst@dji.minjus.nl Netherlands Instituut voor Forensische Psychiatrie en Psychologie (NIFP) | Herman Gorterstraat 5, 3511 EW Utrecht NLD |

Postadres Postbus 13369 I 3507 LJ I Utrecht | T +31 (0)88-0710242.


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