The article discusses the application of diagnostics in forensic examination. Examples of an integrated approach to solving diagnostic problems are shown. The place of the methods of natural and technical sciences in the establishment of identification and diagnostic features is shown. Attention is paid to the tasks of a retrospective nature in conducting forensic engineering and technical examinations, which are aimed at establishing past events, restoring facts, or previous states of the object of research using preserved traces. The concept of reverse engineering is introduced and explained. The areas of its application are outlined.