The objective of the present work was the search for the theoretical foundations and the approaches to the assessment of the methodological basis for the application of the spectral analysis to the investigation of the functional-dynamic complexes (FDC) of oral speech skills for the medical criminalistic identification of the speaker. The study included the analysis of the relevant literature publications, methodological proposals of the authors of the present article, and the results of their medical criminalistics investigations and laboratory experiments. The results of the study give evidence that the spectral analysis provides an acceptable tool for distinguishing the stable identification signs of a given acoustic group that characterize the functional-dynamic complexes of oral speech skills skills for the medical criminalistic identification of the speaker.