As a rule, an expert psychologist can participate in a criminal case in one of two roles. The first one is participation in interviewing a witness if “there is any doubt as to the witness’ mental condition, his/her intellectual development, or ability to perceive or recollect the things perceived”. In this case, the legal grounds for appointment of an expert for this task are found in Art. 192 § 2 of the Polish Code of Criminal Procedure (CPC).
The other role is making statements on the responsibility of the accused (defendant). As set in Art. 202 § 2 of the CPC, the two psychiatrists delivering an opinion on the mental state of the accused may additionally require the appointment of an additional expert or experts of other specialities. This in most cases is an expert psychologist, and at times an expert sexologist. An expert psychologist appointed in this manner delivers an opinion which is an autonomous part of the whole psychiatric opinion.
As much as the opinions of expert psychologists issued after participation in witness interviews are as a rule overrated in practice, and the experts themselves, often acting at the behest of the court, prepare opinions on the credibility of witness’s statements that exceed the scope of their remit set forth in Art. 192 § 2 of the CPC, and furthermore beyond the limits of their psychological competences, the psychological opinions complementing those of the psychiatrists are as a rule undervalued. In these opinions, expert psychologists describe the personality of the accused (defendant), in particular his/her disorders, levels of mental and emotional development, etc.
Even if confirmation of personality disorders were to have no bearing on the assessment of responsibility (sanity), or significantly diminished responsibility (within the meaning of Art. 31 § 1 and § 2 of the Criminal Code), it can be significant for recognising responsibility diminished in a degree lesser than significant, which may at times influence the penalty. According to Art.53 of the Criminal Code, the severity of sentence must not exceed the degree of guilt. Because sanity is an important part of guilt, diminished sanity always means diminished guilt.