The article presents the potential consequences of errors made during the gathering of evidence at the investigative phase of criminal proceedings. In the authors’ opinion, the properly implemented investigative methods could lead to achieving the goal of criminal proceedings as defined under the art. 2 § 1 point 1 of the Code of Criminal Procedure. The authors indicate the course of events, testimonies of witnesses, and a general analysis of the accumulated evidence, which verification at the stage of the court proceeding led to the defendant's final acquittal of the alleged act. The article confirms that conducting the preparatory proceedings is a sum of complicated and indispensable activities and the committed omissions accumulate at the final stage.