CART

Staining blood traces

Staining solutions and reagents used for improving the contrast of marks (fingerprints and footmarks) made in blood.
 

Acid Yellow 7

Main uses: Blood traces on non-porous surfaces
 
Acid Yellow 7 is a dye solution in a water/acetic acid/ethanol mixture that is used for staining fingerprints and shoeprints made in blood. Prints in blood are colored yellow after treatment with Acid Yellow 7. They then fluoresce under blue/blue-green light. Acid Yellow 7 should not be used on absorbent surfaces like paper, carton material, bed sheets, or carpet. It works very well on non-absorbent backgrounds like linoleum, glass, tiles, painted surfaces, or PVC floor covering.
 
Due to a raw material for the dye not being available anymore our suppliers have informed us that Acid Yellow 7 cannot be supplied anymore. Our stock has now run out. We are looking for alternative ways to get hold of it.
 

Acid violet 17

Main uses: Blood traces on non-porous, semi-porous and porous surfaces.
 

Acid Violet 17 (AV17) is a dye solution based on a water/acetic acid/ethanol mixture that is used for staining fingerprints and shoeprints made in blood. Prints in blood are colored purple after treatment with Acid Violet 17 (similar color as LCV or Coomassie Blue). Acid Violet 17 can be used on absorbent surfaces but will stain the background. The CAST manual suggests to test a small part of the item away from the mark with Amido Black and AV17 to see which one gives less background staining.
Acid Violet 17 can be used after Acid Yellow 7 but may show less contrast than would be obtained with AV17 alone.

Before staining, prints in blood should be fixed to prevent them from running (causing loss of detail) when the staining solution is applied. In general fixative is applied before any staining solution except Leuco Crystal Violet, which contains fixative.

 

Amido Black

Amido Black (Acid Black 1) is a dye that stains the protein component of blood blue-black. Amido Black staining solution can be methanol- or water-based. Amido Black in methanol has a greater staining power (compared to the water/citric acid based formulation), but due to the toxicity of the methanol, it is also more dangerous.
 
The formulation from CAST (The Centre for Applied Science and Technology - DSTL - UK) that is based on water/ethanol/acetic acid stains as good as the methanol-based one. For use on a crime scene (for example, shoeprints in blood) the water-based staining solutions are advised.
 
When used on porous or semi-porous surfaces Amido Black will likely produce some background staining. Amido Black will not produce fluorescence.
 

Crowle's stain

Crowle's Stain, is a protein stain like for example Acid Violet 17 and Amido Black. Crowle's Stain colors marks in blood red. It is also known as Crowle's double stain because it contains two dyes: Crocein Scarlet 7B (major component) and Coomassie Brilliant Blue R (minor component).
 
The formulation contains a toxic substance (trichloroacetic acid) and acetic acid but is otherwise water-based.
 
The stained marks can hardly be lifted with a white gelatin lifter and do not fluoresce, either on the treated surface or the gellifter. In comparisons Crowle's stain gives less contrast than Amido Black or Acid Violet 17.

 

Hungarian Red

Main uses: Blood traces on non-porous surfaces
 
Hungarian Red is a water-based staining solution for traces in blood. It has a number of advantages compared to other staining solutions. It is safe (water-based), stains well, and can be lifted with a white gelatin lifter. A special characteristic of Hungarian Red is that the lifted traces fluoresce under green light, making it possible to visualize weak traces, even when they are present on a dark surface.
 

 

Coomassie Blue

Main uses: Blood traces on non-porous surfaces
 
Coomassie Blue, a reagent like Amido Black that stains proteins, is methanol-based. Traces in blood are stained blue to purple.
 
 

Leuco Crystal Violet

LCV (Leuco Crystal Violet), also known as ALCV (Aqueous Leuco Crystal Violet), is a coloring reagent for blood that is based on the blood-catalyzed reaction of hydrogen peroxide with LCV, whereby the colorless LCV is oxidized to the purple crystal violet (the same dye as used in Gentian Violet). Because this oxidation will also occur slowly under the influence of light and oxygen, the contrast of the visualized traces and the background is not permanent. After a period of time the background will also be colored purple.
To maximize the shelf-life, the hydrogen peroxide is separately packaged in an opaque, brown plastic bottle. Before use, the hydrogen peroxide is added to the other solution (in a mixing ratio of 1:4). Both solutions are water-based. The LCV solution already contains fixative, so there is no need to fix blood before staining.
In contrast to other staining solutions, LCV is very suitable for porous surfaces.