The actions carried out at the scene of the event as a result of the possible commission of a criminal act constitute the most important criminal investigation procedures from which it is possible to obtain objective information for the possible attribution of the facts to a certain person or persons. Criminalistics science has been concerned with the theoretical development of the different specialties that make up the criminalistics technique and with the tactical and methodological actions necessary for investigators, experts, doctors and other participants in the examination of the crime scene to execute their process of obtaining the quality evidentiary material. The objective of this study is to describe the basic rules for investigation at the scene, with which the administration of justice in Ecuador will be able to achieve greater effectiveness in the fight against crime at the current stage. The methodology used in the research is nourished by analysis and synthesis, induction and deduction, abstraction and concretion, among other methods that have allowed us to contribute new knowledge to the theoretical development of the topic and propose as a way to improve the criminal investigation the development of a Manual for investigation at the crime scene which must be part of the professional training of investigators, experts, judges and prosecutors.