What is Leucomalachite green primarily used for in criminal investigations?

Leucomalachite green is primarily used in criminal investigations for testing for blood. This chemical reacts with hemoglobin and is part of a colorimetric test that produces a green color upon contact with blood, indicating the presence of this bodily fluid. Its sensitivity and ability to detect even small traces make it a valuable tool in forensic science, particularly at crime scenes where blood may not be immediately visible or where dilution has occurred.

The other options presented do not correspond to the primary application of Leucomalachite green. While DNA testing involves biological material extraction and analysis, the use of Leucomalachite green is specific to blood detection. Gunshot residue testing involves different methodologies, often leveraging chemical compositions from firearm discharge rather than blood components. Similarly, drug detection typically utilizes different reagents and testing methods altogether, focusing on substances other than blood itself.