The high quality of pre-trial and judicial criminal procedure depends on the widespread use of data of technical, natural and other sciences for the purpose of solving crimes. The goal of the research is the search for and determination of modern ways and means of optimizing the activity of persons directing the process, judges, prosecutors and investigators, in solving the tasks of the commission and carrying out forensic psychiatric and forensic mental health assessment in the course of the investigation of crimes. Based on the results of this research, conclusions are drawn, and suggestions are made to improve the Criminal Procedure Law (Latvia), related to the commissioning and carrying out of forensic psychiatric and forensic mental health assessment.