It must be a written request, stating reasons; in case of urgency this can be done verbally, and then to be confirmed in writing within 3 days.
Article 126h DCCP (infiltration) cannot be issued verbally. This measure is regulated by a stringent approval procedure that will take at least 2 weeks.
According to the Dutch implementation law, implementing Article 28 and 29 of the Directive EIO, an additional ground for non-execution applies; if in a similar Dutch criminal case the application of the measure is not possible, this is a reason to refuse the EIO.
Furthermore the public prosecutor can choose another measure then asked for in the EIO, if the requested measure does not exist in Dutch law or would not be applicable.
It is important to thoroughly explain the necessity of the measure asked for.
The measure of systematic undercover gathering of information on the suspect can only be issued for a maximum of three months. This period can be prolonged with tree months (unlimited with view to the investigating needs).For a prolongation an additional request is needed, in which the necessity for the prolongation is explained.
Both other measures will be issued for a certain period, to be defined by the public prosecutor in his order.
In the Netherlands we have the so called Tallon criterium. A person cannot be enticed by the investigating officer to perform a criminal act or omission other than he or she had already planned to do.