The aim of this work is to generate a theoretical physical analysis that could be used as a tool that facilitates the criminalistic function in its objective of clarifying the truth and helping to impart justice. One of the most studied fields of action in the criminal area is related to the scenes of a crime, in which, generally, there are evidences associated with hematic impressions. A drop of blood, in its way towards the ground, follows a trajectory that can be calculated through the laws of Physics, behaving like a body in a fluid. To the extent that this model is more detailed, the position of the blood drop can be described more precisely. A detailed analysis of the displacement in the air of a drop of blood, generated by a cutting wound, is presented. Results could be used to determine the spatial point of origin of a drop of blood from experimental measurements on the hematic impression in crime scene. The proper estimation of this position could be of great help at the moment of a criminal investigation since could serve as an additional evidence offering a clearer vision of the events that occurred, to the judge.