The paper is focused on the theory and practical use of forensic and expert knowledge, especially with an emphasis on the issue of probable conclusions of an expert in criminal proceedings, when the issue of forensic identification and especially the degree of probability conclusions is often addressed. In the process of providing evidence, the issue of the probability of an object or the expression of the probability of the versions considered is also often addressed. When hearings before the court or when preparing an opinion, in many cases the expert is required to express his opinion on the probability of one or the other version, in such cases it is necessary to express a subjective view of the problem being assessed. Probabilistic expression of the identification of an object is often an inevitable stage of knowledge in forensic investigation.