When the establishment or evaluation of an important fact requires obtaining a diagnosis and opinion from a person possessing the necessary professional knowledge, an order is issued for such evidence to be provided by expert witnesses. An expert evaluation is ordered in writing by the body conducting the proceedings. The order specifies the facts to be established or evaluated by experts and the persons to whom the expert's report is to be entrusted. If a particular expert evaluation, especially a more complicated one, comes within the sphere of activity of a definite professional institute or can be carried out within a government agency, such expert evaluation is usually ordered from that institute or agency, which then assigns one or more experts to carry it out.
The judge issues a decree ordering an expert evaluation to be made, usually indicating in the order the name of the expert who, as a rule, is chosen from among the permanent, sworn-in court expert witnesses in a particular professional area. If a more complex expert evaluation is necessary, it is possible to also order the expert evaluation to be made by a particular institution or a group of experts. The order for the appointment of an expert is served on the parties and persons or agencies possessing the objects or the documentation germane to the performance of the expertise, and such persons are bound to make the objects or the documentation available to the expert. Should anyone decline to place the required material at the disposal of the expert, the judge may order such objects seized during a house search.
The expert is criminally liable for the opinion he gives. In accordance with the Slovenian Criminal Code, a prison sentence of up to three years is prescribed for producing a false expert opinion.