The scientific article pays attention to covert investigative (investigative) actions as one of the types of evidence in the process of criminal investigation. The influence of this type of evidence on the speed and objectivity of the pre-trial investigation is considered. Carrying out such actions requires careful preparation of the investigator and the prosecutor, as incorrect obtaining of a permit, conducting covert investigative (search) actions and fixing their results in violation allows furthering declaring the evidence inadmissible. Conducting covert actions restricts the constitutional rights of individuals, and therefore after such actions and consolidation of the result, the suspect, defense counsel must be notified in writing by the prosecutor or on his behalf by the investigator of such actions. The theoretical component of conducting covert actions and the position of scientists on the preservation of information during their conduct are studied, the issue of legal regulation of covert actions and the role of results as evidence is considered. Particular attention is paid to the study of decisions rendered by the Supreme Court of Cassation on acquittals. One of the grounds for upholding the acquittal was to declare the results of covert investigative (search) actions inadmissible. The main violations should include: not declassified material media; the rights are not explained; the legality of the grounds for the action has not been proved, as the relevant resolution of the prosecutor, as well as the decision of the appellate court on permission to carry out audio and video control over the person have not been provided; ignoring the exercise of the right to protection; covert records are interrogations, not intrusions, and others. The speed of reaction is important during the first-priority (urgent) actions during the investigation of criminal proceedings, and therefore the expansion of the powers of some procedural subjects will serve as a positive element in the detection of crimes. At the same time, there is an opinion among practitioners and scholars that the expansion of powers may result in abuse by officials and the information obtained during the covert action will be used for corruption or personal purposes of others.