Recently, the issue of providing evidence in criminal proceedings has gained significant relevance. The outcome of a criminal case heavily relies on the accuracy and clarity with which evidence is presented. This article examines a specific type of evidence: the testimony of a suspect or accused, highlighting its unique features. Notably, the legal definition of the subject of such testimony is not explicitly outlined in the law. Furthermore, it is important to recognize that the legislative regulation of testimony differs from the procedural status of the individual being interrogated. Interestingly, the legislator assigns less legal weight to the confession of the accused compared to other forms of evidence. Three levels of the subject of proof in criminal cases were identified. In conclusion, it is emphasized that a clear distinction must be made between the content of testimony subject to proof in a criminal case and the information required to substantiate only the procedural circumstances of the case.