Pre-trial investigation

The investigation of an offence begins with the pre-trial investigation. It is carried out by pre-trial investigation authorities, usually the police. Other pre-trial investigation authorities are the Finnish Border Guard, Customs and the Finnish Defence Forces. The prosecutor is not a pre-trial investigation authority.

The pre-trial investigation involves questioning and the acquisition of other evidence. Coercive measures such as arrest, house search and preventive seizure of an object may be used during the pre-trial investigation. The prosecutor and the pre-trial investigation authority cooperate so that the suspected offence is investigated sufficiently thoroughly.

After the pre-trial investigation, the matter is transferred to the prosecutor for a consideration of charges unless it has become evident during the pre-trial investigation that no offence has been committed. During the consideration of charges, the prosecutor weighs the evidence obtained during the pre-trial investigation and decides whether to bring charges for an offence or not.

If the pre-trial investigation has been deficient, the prosecutor requests the pre-trial investigation authority to carry out further investigations.

Decision on pre-trial investigation

Pre-trial investigation must in general be started when there is cause to suspect an offence. The decision to start a pre-trial investigation is made by the head of the investigation, who is usually a pre-trial investigation authority.

However, the prosecutor usually acts as the head of the investigation in all those cases in which an offence committed by a police officer is investigated. If the suspected offence was committed during a police officer's free time, the prosecutor may, at his or her discretion, transfer the role of the head of the investigation to a pre-trial investigation authority.

Upon the request of the prosecutor, a pre-trial investigation authority must always carry out a pre-trial investigation or a pre-trial investigation procedure.

Restriction of the pre-trial investigation

Even before the consideration of charges, the prosecutor may decide to waive or discontinue the pre-trial investigation at the proposal of the head of the investigation, even if there is cause to suspect that an offence has been committed. This is referred to as restriction of the pre-trial investigation. In such a case, the prosecutor assesses that he or she would not bring charges anyway, even if the pre-trial investigation were to be completed.

The restriction of the pre-trial investigation may be based on, for example, the minor nature of the offence, the perpetrator being underage, a penalty being unreasonable or purposeless, or that sufficient evidence would not be obtained during the pre-trial investigation. A decision to restrict the pre-trial investigation can also be made when the costs of the pre-trial investigation would be too high relative to the nature of the offence.