The present investigation arises from the need to investigate and to experiment scientifically if the contaminants established as controlled variable and not contralada can affect performing the procedure described in clause 4 1 of guide 2DC-GU-0024 on performing ballistic testing on weapons firearms pneumatic gas black powder detonating electrical etc and entering ballistic identification systems It can be reasonably inferred that by performing the forty-two tests manipulating solutions A and B of the Griess reagent it is evident that the pollutants transferred to the Interior of the Cannon 4-stroke oil diesel and gasoline do not affect the results for the identification of nitrites Product of combustion during the Shooting phenomenon Case contrary It happens with rainwater since it is observed that the same it affects the elaboration of the test taking into account that without coming into contact with the gunpowder results in a faint pink coloration indicating in a preliminary way that it is Positive for presence of nitrite