Leucomalachite Green (LMG) was a popular blood reagent used from at least the 1950’s thru the 1990’s. I’m sure some CSIs may still use this reagent but it is not nearly as prolific today.
Most US forensic supply companies don’t even sell the LMG reagent anymore. LMG has two primary uses in crime scene work.
The first is as a presumptive blood test. LMG crystals are mixed with Sodium Perborate, water, and Glacial Acetic Acid (GAA). It’s this last component that made using the reagent a bit unpleasant. It’s the (GAA); it has a pungent vinegar odor which stinks to high heaven.
The sensitivity of this reagent has been reported to be anywhere from 1:5,000 to 1:25,000 parts dilution. LMG is a good reagent for blood because it doesn’t have many false positive reactions. But, there are some concerns that the reagent is a carcinogen (cancer causing) and thus, it is not used much anymore.
If you are writing a novel set in the 1950’s to 1990’s you can consider mentioning this reagent in your storyline.
Watch the video below to see how the testing is conducted. The end of the video also has an interesting observation about the fluorescence of certain food items that may look like blood under normal lighting conditions.