At the initial stage of the criminal procedure, preparatory proceedings are instituted and conducted. They can be commenced as a result of a report made to the police or to the prosecutor's office by an aggrieved party or other people, or as a consequence of obtaining own information by prosecution agencies, justifying the suspicion that a crime has been committed.

The aims of the preparatory proceedings are defined as follows:

1. Establishment whether a prohibited act has been committed and whether it constitutes a crime (because sometimes a given deed, even though prohibited, is not considered a crime- for instance due to the circumstances of self-defence or state of necessity).
2. Identification and, if needed, apprehension of the perpetrator.
3. Collection of data about the perpetrator (age, family relations, financial status, education, criminal record...), and about his or her personal features and characteristics, current lifestyle.
4. Clarification of the circumstances of the case, including identification of the aggrieved parties and the scope of damage.
5. Collection, securing and recording of evidence to the extent necessary to confirm the legitimacy of bringing the indictment or other conclusion of the proceedings, as well as to file a motion for admission of evidence and its examination before the court.

Preparatory proceedings are always conducted or supervised (when conducted by the police) by a prosecutor. Thus, a prosecutor is the "host" of this stage of the proceedings and is entitled to decide on many important issues: for example on levelling a charge, bringing the indictment to court or securing particular evidence.

Depending on various factors, specified in the Code of Criminal Procedure, preparatory proceedings can be conducted as "investigation " or "inquiry ". Generally speaking, investigation is usually conducted by a prosecutor in case of more serious crimes. The parties of the preparatory proceedings are an aggrieved person and a suspect (at this stage, there is not a "defendant").

Both an aggrieved person and a suspect, before the first hearing in such a character, ought to be notified of their rights.

[Legal status as at July 2015]