The article concerns the issue of assessing evidence from an expert opinion in a Polish criminal trial, carried out on the basis of art. 201 of the Code of Criminal Procedure The author focused on explaining the concept of "incompleteness" of opinions and the procedure for verifying such an opinion. According to the author, the current wording of the provision is not controversial when it comes to understanding the concept of "incomplete" opinion. In his opinion, however, it is justified to amend Art. 201 of the Code of Criminal Procedure and explicit acceptance that in the event of deficiencies in the opinions referred to in this provision, it is obligatory to summon current experts or appoint other (new) experts. According to the author, the possibility of confronting experts should also be explicitly allowed, but this should be linked to the assessment of the content of the opinions submitted by them in a given case.