The article presents the results of a study of the legal and scientific aspects of appealing against illegal actions of officials of the investigation and inquiry bodies by the defense party. This problem is multidimensional and includes such components as constitutional and legal foundations, criminal procedural regulation and scientific support of the right to appeal against illegal procedural actions as a mechanism for overcoming violations of the rights of suspects/accused at the stage of preliminary investigation. One of the most common forms of such violations are unjustified refusals to exercise the procedural rights of suspects/accused, in particular, to provide evidence, participate in proving, and familiarize themselves with the case materials. The consequences of such a violation may be expressed in the inability to properly build a defense, including from unjustified charges and, as a result, illegal detention, detention or detention, bringing a knowingly innocent person to criminal responsibility or illegal initiation of a criminal case, pronouncing a knowingly unjust verdict, decision or other judicial act. These violations are obviously complex in nature and hinder the implementation of the principle of equality and competitiveness of the parties in criminal proceedings. Unfortunately, investigators and interrogators often deny the defense the right to present evidence and attach it to the criminal case, and to ensure this, they deny the accused and the defender the right to familiarize themselves with the case materials, while using loopholes in legislation and vague (sometimes too broad) interpretations in the guidelines of judicial interpretation. This leads to the fact that there is no alternative to the prosecution’s version and, of course, to a significant violation of the rights of the accused as participants in criminal proceedings. The negative consequences of this may be cases of unjustified accusation and conviction of innocent persons, the occurrence of other grave consequences (for example, the illness of an unlawfully accused /convicted person, causing property damage during the confiscation of property based on a false accusation, the application of other property sanctions, discrediting and defamation of such a person, etc.). In addition, of course, this practice it causes serious damage to the authority of the court, law enforcement agencies, and the formation of negative public opinion about them. The article analyzes in detail the cases of refusals to present and attach evidence, familiarization with the case materials, examines the “argumentation” given by the staff of the preliminary investigation bodies, judges, and clearly proves its fallacy, using the example of cases that have a great public resonance and the author’s personal experience as a lawyer in such cases. Criminal procedural means of countering such violations are being investigated. In conclusion, based on the conducted research, the author formulates a conclusion aimed at overcoming the accusatory bias and violations of the rights of participants in court proceedings in cases with public resonance, improving and increasing the effectiveness of preventing violations of the constitutional right to defense and adversarial parties.