Undercover operations: valuable but unpredictable investigative instruments

Undercover operations have important value for investigations. In some cases, they provide results that probably could not have been obtained, or only with greater difficulty, with other investigative instruments. Furthermore, the undercover operations that have been carried out do generally pass review by the courts. At the same time, the aspect of unpredictability constitutes an important common characteristic of undercover operations. For example, agreements between undercover agents and suspects for criminal transactions are often not complied with. This is evident from the research performed by the Research and Documentation Centre (WODC), which was today sent to the Lower House by Minister Hirsch Ballin.

WODC research

During an undercover operation, an investigating officer will act as an investigating officer without identifying himself as such during contact with a subject, i.e. a suspect or a person in the circle of people around the suspect. When doing so, the undercover agent plays a role, for example, that of a fellow criminal, and in that capacity tries collect information against or on the suspect. Police actions such as deploying decoy bicycles or cars do not belong to undercover powers.

The WODC performed an investigation into the regulation, implementation and results of this type of investigative instrument. The investigation comprised, inter alia, a study of the legislation and regulation in the Netherlands and abroad, an analysis of dozens of cases in which an undercover operation was implemented, and interviews with, inter alia, Public Prosecutors, members of the criminal investigation services and team leaders of infiltration teams.

Deployment of undercover operations and the value for the investigation

In 2004, undercover operations were implemented in 34 Dutch investigations. Of those 34 undercover operations, 12 contributed to the investigation and/or conviction. That contribution consists, in 7 cases, of evidence that was obtained by means of the undercover operation and that played a role in the conviction of the suspects. In 4 cases, the undercover operation led precisely to the exclusion of suspects; i.e. the investigative team arrived at the conclusion – via the operation – that the original suspicion was (partially) incorrect or less serious than was originally thought. This is a very valuable result, because as a result of this information, the investigation can focus on other suspects, or can be stopped. In 1 case the undercover operation resulted only in steering information: it provided an image of the criminal group and facilitated the deployment of other investigative instruments.

A comparison of the results of the undercover operations with the results of other investigative instruments is very difficult, or cannot be made at all. It is therefore impossible to answer the questions of whether the identified results of undercover operations are 'good' or 'bad'. It is clear that, in cases in which the operation led to evidence or exclusion, that result often could not, or in any case less easily, have been achieved with other instruments.


A remarkable shared characteristic of undercover operations is the unpredictability with which they often take place. For example, intended pseudo buys do not – in the majority of the cases investigated – occur according to the previously-made plans or agreements. A pseudo buy is generally a criminal transaction between an undercover agent and a subject, whereby the first party buys, for example, drugs or weapons from the latter party. Although a portion of the pseudo buys ultimately result in important evidence against a suspect, another portion does not go ahead at all - for example because the suspect cannot or will not supply, or because the goods have already been sold; or the pseudo buy does go ahead but only after a previous failed attempt or on a smaller scale, for example a smaller amount of drugs than expected.


An investigation of court decisions shows that the objections put forward by lawyers against undercover operations are usually rejected by judges. Transparent reporting by the police and the Public Prosecution Service – and the insight into undercover operations that is provided to judges as a result – plays an important role in that context.

Additional information on the investigation

The Dutch Code of Criminal Procedure distinguishes three undercover powers: the structural collection of information, the pseudo buy/provision of services, and infiltration. As stated above, in 2004 undercover operations were implemented in 34 Dutch investigations. In that year, it exclusively concerned the structural collection of information and pseudo buys/service provision. With respect to infiltration, information over several years was collected, namely the period 2000-2005. During that period, infiltration was deployed in 14 Dutch cases. Information about those operations can be found in the report on the investigation.

Response from the Minister of Justice

In his response to the investigation, Minister Hirsch Ballin writes to the Lower House that the undercover operations in the cases investigated made a significant contribution to the investigation, despite the difficult circumstances in which they have to be performed. The investigation shows that the unpredictable criminal environment has made an impact on the results of undercover operations. There are many unexpected developments that influence the chances of success of the operation, because undercover operations take place in an uncontrolled social environment. Undercover powers are nearly exclusively deployed in cases that are hard to prove and cases in which other investigative resources have proved insufficient. In the cases in which the operational objective of the deployment of an undercover agent is not fully achieved, the so-called steering and/or residual information (still) make an important contribution to the investigation, for example because other suspects or offender groups are identified.

The Public Prosecution Service has indicated that it requires expansion of the available investigative methods in very specific situations, and will send a note in that connection to the Ministry. In his letter, the Minister announces that he will send this note together with his response to it to the Lower House in the summer of 2010.