The preliminary investigation stage, as the cornerstone of criminal proceedings, is the most sensitive phase of the criminal process, because it is at this stage that the foundations of the accusation are formed and evidence is collected. Violation of the defendant's defense rights at this stage not only harms the defendant personally, but also undermines the integrity of the entire criminal justice process and may lead to unjust verdicts. Therefore, effective protection of the defendant's rights during preliminary investigations and ensuring compliance with the principles governing proceedings at this stage are of fundamental importance. Such protection becomes practical and meaningful only when appropriate and effective enforcement guarantees for violations of these rights are anticipated and properly implemented.

Enforcement guarantees are tools that ensure the effective application of legal rules and, in fact, distinguish law from other social norms. Without enforcement mechanisms, legal rules would remain merely moral recommendations and lose their binding and coercive force. In the context of criminal proceedings, enforcement guarantees are generally divided into two main categories. The first category consists of guarantees related to the conduct of proceedings, including the nullity of unlawful actions and the inadmissibility of illegally obtained judicial evidence. The second category relates to guarantees directed at those who violate procedural principles, which may take the form of criminal, civil, or disciplinary liability.For instance, when judicial officers conduct a vehicle search in non-flagrant crimes in violation of privacy and without prior authorization from a judicial authority, the evidence obtained through such an unlawful search is inadmissible, and the court is obliged to render a verdict of acquittal. This example clearly illustrates the crucial role that enforcement guarantees play in safeguarding the defendant’s defense rights.Nevertheless, despite the importance of this issue, several aspects of enforcement guarantees concerning violations of the defendant’s defense rights during the preliminary investigation stage remain ambiguous and require further examination.