On what surfaces can it be used

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 [1]. 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.

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.

How to fix the prints

Fixing is best done with a 2% solution of sulfosalicylic acid in water (20-23 gram in 1 liter). To make sure the print in blood is thoroughly fixed, we recommended the following method using absorbent paper (like filter paper, tissue paper, or paper towels) and a wash bottle containing sulfosalicylic acid solution.

Take a dry piece of the absorbent paper that is sized to cover the print(s). Hold it directly over the print-area, parallel to the surface and just slightly above the surface. To begin fixing, drop one edge of the paper to the surface and moisten heavily along its entire length, so that it is anchored and will stay in place.

Starting from that edge, wet the paper progressively further while smoothing the wetted part onto the print and minimizing trapped air bubbles. Work carefully from one edge to the other. When possible, for example, with an object or with a print on an angled surface start from the top and work downwards.

Once the wet paper entirely covers the print, leave it there for a minimum of three minutes.When the blood is a thick layer, leave the paper there 5 minutes or more. Remove the paper. An excess of fixative can be rinsed away with water, but this is not necessary.
When the blood is relatively fresh, you will notice that fixing changes its color from dark red to dark brown.

Staining procedure

Once the print is fixed, it can be stained with Acid Yellow 7 solution. Use a wash bottle to apply the solution to the article or area of interest. With fingerprints, a disposable pipet can be used. Alternatively you can submerge the article in a container/bath of solution if the size of the article permits.

Spraying is technically feasible but will likely raise the amount of ethanol vapor in the air. Sufficient protection measures should be taken to avoid inhalation of aerosols.
After the staining solution is applied leave it in contact with the print for 1-3 minutes. Then wash the surface with the same water/acetic acid/ethanol mixture as used for the dye solution, but without the dye.

Alternatively, water can be used but may result in more background staining. If the print is located on a floor, the wash solution might be removed with a vacuum cleaner that can handle water. Otherwise, remove it with paper towels or the like.

Lifting and fluorescence

Acid Yellow 7 not only has a good staining capacity but has some special characteristics.The stained prints will fluoresce when excited with blue and blue-green light though the fluorescence will be faint. To obtain the best result, eliminating backgrounds and/or background fluorescence, stained prints can be lifted with a white BVDA Gellifter.

Before lifting with the white Gellifter, the area should be completely dry. Be very careful not to trap air bubbles under the lifter surface. Leave the lifter on the print for only a short time, something like a minute. Photograph within a couple of hours after lifting as the dye will slowly diffuse in and across the surface of the lifter, thereby blurring the print.
Lifting can be done more than once, with or without re-staining between lifts. Repeat lifting/staining in important cases.

Fluorescence is excited with blue and blue-green light (400-490 nm) and visible even when using long-wave UV. The filter used in front of the lens depends on the excitation wavelength: clear for UV to yellow/light orange for the higher wavelengths.

Safety

Acid Yellow 7 powder is not labeled as a hazardous preparation. Since its working solution is based on a water/ethanol mixture, no harmful fumes are liberated in normal use, although the acetic acid smell might be irritating. When large amounts are used and/or the temperature is high enough, a potentially explosive air/ethanol vapor mixture can result unless ample ventilation is provided. Acid Yellow 7 solution will color the skin and clothing.

Sulfosalicylic acid crystals are labeled as an irritant substance but the 2% solution is not labeled as a hazardous product. Given the fixative effect on blood, we strongly advise wearing gloves (vinyl gloves will suffice) when using it.

Avoid breathing aerosols (mists) and vapors of the fixative, washing liquid, and Acid Yellow 7 solution. Likewise avoid contact with solutions and the Acid Yellow 7 powder. Wash your hands after each session, especially before eating or drinking.

Composition of the solutions

Acid Yellow 7

Preferably use an Erlenmeyer flask for preparation of the Acid Yellow 7 solution. Add water first and dissolve the Acid Yellow 7 powder in the water by swirling the flask or using a magnetic stirrer and a PTFE-covered stir bar. The powder will dissolve quickly. Then add ethanol and acetic acid (order not important.)

Blood fixative

Add components to a beaker/flask of suffient size and mix till complete dissolution, using a magnetic stirrer.

Washing solution

References and footnotes

[1] Sears, V.G.; Butcher, C.P.G.; Fitzgerald, L.A. "Enhancement of Fingerprints in Blood, Part 3: Reactive Techniques, Acid Yellow 7, and Process Sequences." Journal of Forensic Identification 2005, Vol. 55, No. 6, p. 741-763.

On what surfaces can it be used

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 [1]. 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.

How to fix the prints

Fixing is best done with a 2% solution of sulfosalicylic acid in water (20-23 gram in 1 liter). To make sure the print in blood is thoroughly fixed, we recommended the following method using absorbent paper (like filter paper, tissue paper, or paper towels) and a wash bottle containing sulfosalicylic acid solution.

Take a dry piece of the absorbent paper that is sized to cover the print(s). Hold it directly over the print-area, parallel to the surface and just slightly above the surface. To begin fixing, drop one edge of the paper to the surface and moisten heavily along its entire length, so that it is anchored and will stay in place.

Starting from that edge, wet the paper progressively further while smoothing the wetted part onto the print and minimizing trapped air bubbles. Work carefully from one edge to the other. When possible, for example, with an object or with a print on an angled surface start from the top and work downwards.

Once the wet paper entirely covers the print, leave it there for a minimum of three minutes.When the blood is a thick layer, leave the paper there 5 minutes or more. Remove the paper. An excess of fixative can be rinsed away with water, but this is not necessary.
When the blood is relatively fresh, you will notice that fixing changes its color from dark red to dark brown.

Staining procedure

Once the print is fixed, it can be stained with Acid Violet 17 solution. Use a wash bottle or the spray bottle in which it is supplied to apply the solution to the article or area of interest. With fingerprints, a disposable pipet can be used. Alternatively you can submerge the article in a container/bath of solution if the size of the article permits.

Spraying is technically feasible but will likely raise the amount of ethanol vapor in the air. Sufficient protection measures should be taken to avoid inhalation of aerosols.
After the staining solution is applied leave it in contact with the print for 1-3 minutes. Then wash the surface with the same water/acetic acid/ethanol mixture as used for the dye solution, but without the dye.

Alternatively, water can be used but may result in more background staining. If the print is located on a floor, the wash solution might be removed with a vacuum cleaner that can handle water. Otherwise, remove it with paper towels or the like.

Lifting and fluorescence

Acid Violet 17 can be lifted with a white gelatin lifter (takes much more time than Acid Yellow 7 - around 15 minutes instead of a few minutes with AY7.) The stained prints will fluoresce when excited with green light though the fluorescence will often be faint. To obtain the best result, eliminating backgrounds and/or background fluorescence, stained prints can be lifted with a white BVDA Gellifter.

Before lifting with the white Gellifter, the area should be completely dry. Be very careful not to trap air bubbles under the lifter surface. Leave the lifter on the print for quite some time, something like 15 minutes. Photograph within a couple of hours after lifting as the dye will slowly diffuse in and across the surface of the lifter, thereby blurring the print.
Lifting can be done more than once, with or without re-staining between lifts. Repeat lifting/staining in important cases.

Fluorescence is excited with green light (480-545 nm). A red filter is used in front of the lens.

Safety

Acid Violet 17 powder is not labeled as a hazardous preparation. Since its working solution is based on a water/ethanol mixture, no harmful fumes are liberated in normal use, although the acetic acid smell might be irritating. When large amounts are used and/or the temperature is high enough, a potentially explosive air/ethanol vapor mixture can result unless sufficient ventilation is provided. Acid Violet 17 solution will color the skin and clothing.

Sulfosalicylic acid crystals are labeled as an irritant substance but the 2% solution is not labeled as a hazardous product. Given the fixative effect on blood, we strongly advise wearing gloves (vinyl gloves will suffice) when using it. Wearing protective goggles is not a bad idea either.

Avoid breathing aerosols (mists) and vapors of the fixative, washing liquid, and Acid Violet 17 solution. Likewise avoid contact with solutions and the Acid Violet 17 powder. Wash your hands after each session, especially before eating or drinking.

Composition of the solutions

Acid Violet 17

Preferably use an Erlenmeyer flask for preparation of the Acid Violet 17 solution. Add water first and dissolve the Acid Violet 17 powder in the water by swirling the flask or using a magnetic stirrer and a PTFE-covered stir bar. The powder will dissolve quickly but due the strong color of the solution this will be hard to see. Allow enough time to dissolve all the dye. Then add ethanol and acetic acid (order not important.) Dissolving the Acid Violet 17 first in the ethanol/acetic acid mixture and then diluting it with water is also possible (as is dissolving it in the complete mixture of course.)

Blood fixative

Add components to a beaker/flask of suffient size and mix till complete dissolution, using a magnetic stirrer.

Washing solution

References and footnotes

[1] Sears, V.G.; Butcher, C.P.G.; Prizeman, T.M. "Enhancement of Fingerprints in Blood - Part 2: Protein Dyes" Journal of Forensic Identification 2001, Vol. 51, No. 1, p. 28-38.

Amido Black (Acid Black 1) is een kleurstof die eiwitten, zoals aanwezig in bloed, blauw-zwart kan kleuren. Amido Black wordt zowel op methanol basis als op water- en water/ethanol/azijnzuurbasis geleverd. Amido Black in methanol kleurt sterker, maar is door de giftigheid van de methanol ook gevaarlijker. Amido Black (Acid Black 1) is a dye that can stain proteins, such as those present in blood, blue-black. Amido Black can be supplied as methanol-based, water-based, and water/ethanol /acetic acid base. Amido Black in methanol stains more strongly than the water-based formulation, but is also more dangerous due to the toxicity of the methanol.
 
CAST's (The Centre for Applied Science and Technology - formerly part of the Home Office, now DSTL - UK) water/ethanol/acetic acid-based formulation stains as well as the methanol-based one. Especially for use on a crime scene (e.g. shoe marks in blood), the water/ethanol/acetic acid- or water-based Amido Black (the latter formulation stains less strongly) is therefore recommended.
 
When using Amido Black on porous or semi-porous surfaces, it is likely to give some background coloration. Amido Black does not fluoresce.

On what surfaces can it be used

Amido Black (Acid Black 1) is a blue-black dye used in various formulations on both non-porous, semi-porous and porous surfaces for staining traces in blood.
The formulations we offer are based on:

• methanol
• water/citric acid
• water, ethanol, and acetic acid [1]

The methanol-based one is the oldest (since the 1970s according to ref. 1), the acetic acid-based water/ethanol one the newest ([1], 2000). The CAST manual [2] recommends testing both Amido Black and Acid Violet 17 on a small piece of a porous or semi-porous item, away from where a trace is suspected, to see which of the two causes the least background staining.
Amido Black cannot be used after staining with Acid Yellow 7 [ref. 2, page 5-AD2]. It then stains much less strongly than Acid Violet 17.

Before using Amido Black, whatever formulation is used, the blood traces must first be fixed to avoid running through the trace (loss of detail).

Fixing blood traces

Fixation can be done with a 2% solution of 5-sulphosalicylic acid in water (20-23 grams in 1 litre of demi-water or distilled water). To ensure that the blood trace is well fixed, we recommend the following method that uses absorbent paper (such as filter paper, tissues, paper towels) and a spray bottle with sulphosalicylic acid solution.

Take a dry piece of absorbent paper large enough to cover the print to be fixed. Hold the paper above the print, parallel to the surface and then drop one side of the paper onto the surface (e.g. a short side if it is a shoe print). Soak this part with fixer solution all over the side, this part now acts as a kind of anchor.

Now wet the entire paper with the spray bottle, starting from the side that is already on/along the print, and keep lowering the wet part onto the print. This will prevent air bubbles from getting between the paper and the print as much as possible. Work slowly (the paper expands when it gets wet) and if the print is at an angle in the vertical plane (or can be kept that way) start on the high side and work down.

When the wet paper covers the entire track, leave it for 5 minutes. When the blood is a thick layer longer (deeper layers may not be fixed!). Then remove the paper. Fixative left on the trace can be washed away with water, but it is not necessary.
When the blood is relatively fresh, a colour change from dark red to dark brown will have occurred.

Method for staining

Once the print is fixed, it can be stained with the Amido Black solution. Use a spray bottle or wash bottle to apply the dye solution. With fingerprints, a pipette can be used or with an object of not too large size by dipping into a container/bath with dye solution.

Using a spray bottle has the disadvantage over using a wash bottle that methanol or ethanol vapour (depending on which formulation is used) will be released into the air. This is a health hazard in the case of methanol. Using a dust mask to prevent inhalation of the spray mist is also recommended.
After the dye solution is applied, leave it in contact with the print for about 3 minutes. Then rinse the surface with the same solvent mixture as used for the dye solution.
Methanol/acetic acid in the case of the methanol formulation, water or water with vinegar or citric acid in the case of the water-based formulation and water/ethanol/acetic acid in the case of the that formulation. For the methanol/acetic acid-based formulation, there is a second rinsing solution: a 5% acetic acid solution (vinegar).

If the prints are on the floor, the rinsing solution can also be sucked away with a wet and dry vacuum cleaner. Absorbent paper as applied in fixation can also be used to collect the liquid. Blowing away the solutions with an air jet is also an option.

Lifting

Prints stained with Amido Black do not fluoresce, neither after lifting with a white gelatin lifter. Lifting enables the elemination of backgrounds and/or background fluorescence.

Before lifting can be done with a white gelatin lifter the print (on a non-porous surface) needs to be dry. When applying the lifter make absolutely sure that are no air bubbles trapped between the stained print and the lifter. Leave the lifter on for quite some time, in the order of 15 minutes. Photografing the lifted print should be done within a few hours. This is because the dye will slowly diffuse through the lifter in all directions. The print will lose sharpness as a result.
Lifting the print can be done several times, with or without re-staining in between. In important cases, it is advisable to try lifting and re-staining several times.

Safety

Amido Black powder is irritating to the skin, eyes and respiratory tract and can cause serious eye damage/eye irritation. In solution, of course, there is no longer a respiratory hazard but eye protection is definitely recommended. Depending on the formulation, there is vapour hazard (not with the water/citric acid-based Amido Black solution). In fact, the methanol formulation can only be used in a fume cupboard. On a crime scene, the methanol vapour is too dangerous.
The working solutions and rinsing solution based on the water-ethanol mixture will not form harmful vapours in normal use, although the vinegar smell may be irritating. When using large quantities or when the temperature is high enough, a potentially explosive ethanol-air mixture may be formed with insufficient ventilation. Furthermore, Amido Black solutions stain skin and clothing. Use of gloves is therefore necessary (nitrile gloves with the methanol formulation).

5-Sulfosalicylic acid powder has been characterised as an irritant, but the 2% solution is not a dangerous mixture. However, given its fixing effect on blood, we still recommend wearing gloves (nitrile, vinyl or latex gloves suffice) when using it. Use of goggles is also advisable.

Avoid inhaling sprays (aerosols). By the way, the fixative solution does not emit fumes. Wash hands after every use of fixative, dye or rinse solution, especially before eating or drinking.

Composition of solutions

Methanol-based Amido Black

Preferable use an Erlenmeyer flask for making the Amido Black solution. The order in which methanol and acetic acid are added to the weighed amount of Amido Black powder is not important. Dissolve it using a magnetic stirrer and a stirring bar (magnet covered with PTFE). The powder dissolves slowly but the strong colour of the solution will make it difficult to see. Take enough time to allow the powder to dissolve (half an hour, for example).

For the methanol-based rinsing solution, the same quantities of solvent as for the working solution are used with omission of the Amido Black powder.
The second rinsing solution (5% vinegar) is made by diluting 50 ml of glacial acetic acid with 950 ml of demineralised or distilled water.

Water/ethanol/acetic acid-based Amido Black

Preferable use an Erlenmeyer flask for making the Amido Black solution. The order in which methanol and acetic acid are added to the weighed amount of Amido Black powder is not important. Dissolve it using a magnetic stirrer and a stirring bar (magnet covered with PTFE). The powder dissolves slowly but the strong colour of the solution will make it difficult to see. Take enough time to allow the powder to dissolve (half an hour, for example).

For the water/ethanol/acetic acid-based rinsing solution, the same volumes of solvent as for the working solution are used with the omission of the Amido Black powder.

Blood fixative

Add the components together in a beaker or flask/bottle of sufficient size and mix until everything is dissolved. Use of a magnetic stirrer with stirring bar is recommended.

References and footnotes

[1] Sears, V.G.; Prizeman, T.M. "Enhancement of Fingerprints in Blood - Part 1: The Optimization of Amido Black" Journal of Forensic Identification 2000, Vol. 50, nr. 5, p. 470-480.
[2] Fingermark Visualisation Manual, Chapter 5.PD ISBN: 978-1-78246-234-7, Home Office, January 2014. No longer available at The Stationary Office.

How to use Hungarian Red

On what surfaces can it be used

Hungarian Red is a dye (Acid Fuchsin) solution in water/acetic acid mixture that is used for staining fingerprints and footprints made in blood. Prints in blood are colored red after treatment with Hungarian red. Hungarian Red should not be used on absorbent surfaces like paper, carton materials, bed sheets, or carpet. It works very well on non-absorbent backgrounds like linoleum, glass, tiles, painted surfaces, or PVC floor covering.

Fix prints in blood before staining

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.

How to fix the prints

Fixing is best done with a 2% solution of sulfosalicylic acid in water (20-23 gram in 1 liter). To make sure the print in blood is thoroughly fixed, we recommended the following method using absorbent paper (like filter paper, tissue paper, or paper towels) and a wash bottle containing sulfosalicylic acid solution.

Take a dry piece of the absorbent paper that is sized to cover the print(s). Hold it directly over the print-area, parallel to the surface and just slightly above the surface. To begin fixing, drop one edge of the paper to the surface and moisten heavily along its entire length, so that it is anchored and will stay in place. Starting from that edge, wet the paper progressively further while smoothing the wetted part onto the print and minimizing trapped air bubbles. Work carefully from one edge to the other. When possible, for example, with an object or with a print on an angled surface start from the top and work downwards.

Once the wet paper entirely covers the print, leave it there for a minimum of three minutes. When the blood is a thick layer, leave the paper there 5 minutes or more. Remove the paper. An excess of fixative can be rinsed away with water, but this is not necessary.

When the blood is relatively fresh, you will notice that fixing changes its color from dark red to dark brown.

Staining procedure

Once the print is fixed, it can be stained with Hungarian Red. The most economical way is using the sprayer. Spraying always causes some mist (aerosol) that will float around in the air. Especially when you stain large areas, do use some respiration protection. Alternatively, you can use a wash bottle (or with fingerprints even a disposable pipet).

After the staining solution is applied by sprayer or wash bottle, leave it in contact with the print for about one minute. Then wash the surface with water (or a 5% water/acetic acid mixture = 19:1 volume/volume ratio). If the print is located on a floor, the wash water might be removed with a vacuum cleaner that can handle water. Otherwise, remove it with paper towels or the like.

It is advantageous to immediately remove the water and water droplets from the processed area after rinsing, with compressed air or a powerful blower. If water droplets remain on the print, you will notice that some dye will dissolve in them. After drying that will be visible (possible loss of detail).

Lifting and fluorescence

Hungarian Red not only has a good staining capacity but has also some special characteristics. Stained prints can be lifted with a white BVDA gelatin lifter so that backgrounds are eliminated and/or parts on dark backgrounds become visible. The lifted print will also fluoresce, whereby details or prints that were hardly visible with the naked eye are now easily discernible in fluorescence.

Before lifting with a white gelatin lifter, the area should be completely dry. Be very careful not to trap air bubbles under the lifter surface and leave the lifter on for 15-30 minutes. Photograph within a couple of hours after lifting (the dye will slowly diffuse in and across the surface of the lifter, thereby blurring the print).

Lifting can be done more than once, with or without re-staining between lifts. Repeat lifting/staining in important cases.

Fluorescence is excited with green light (515-560 nm) and the filter used in front of the lens is a red filter (Kodak Wratten 25, a barrier filter of about 600 nm or a long-pass filter with cut-on of about 600 nm).

Safety

Hungarian Red is not labeled as a hazardous preparation. Since it is water based, no harmful fumes are liberated in use, although the acetic acid smell might be irritating. It will color the skin, although this will not last very long (in our experience less than a day). Contaminated clothing will be stain-free after regular washing.

Avoid breathing aerosols (mists) of both the fixative and Hungarian Red. Likewise avoid contact with solutions and wash your hands after each session, especially before eating or drinking.

Effect on DNA analysis

According to a Canadian study useable DNA can still be retrieved from treated prints after staining with Hungarian Red.

Leuco Crystal Violet (LCV) for staining of marks in blood

Leuco Crystal Violet (LCV) is a reagent for the detection and staining of marks in blood. It is a colorless to light-blue water-based (400 ml in a brown glass bottle, solution A) that is mixed just before use with the included 15% hydrogen peroxide solution (100 ml in a brown plastic bottle). The mixing ratio is 4 parts solution A to 1 part peroxide solution (B).

The reagent is sprayed over the surface where marks in blood are suspected. When the (mixed) reagent comes in contact with blood the hydrogen peroxide is broken down by the hemoglobine. In turn the oxidized hemoglobin oxidizes the the colorless LCV to strongly purple-colored crystal violet. The hemoglobin is now back in it's original state and can be oxidized by hydrogen peroxide again. This is therefore a catalytic reaction (the hemoglobin is the catalyst).

Crystal violet is also known as gentian violet and Basic Violet 3. On non-porous surfaces rinsing with demineralized water to remove excess reagent (which will slowly become purple due to oxidation by air helped by light of the unreacted LCV) is an option.

Once the oxidation to crystal violet has occurred, removing the purple stain is often cumbersome if not impossible. This should be kept in mind when using it on crime scenes.

Advantages of the reagent are:

• in principle there is no need for rinsing which makes it less labor intensive than for instance dye solutions like Amido Black and Hungarian red and makes it possible to use it on materials that do not lend themselves to rinsing like carpet.
• it can be used both on porous and non-porous surfaces.
• the marks do not need prior fixing because the reagent already contains fixative (the working solution contains 2% sulfosalicylic acid).
• it does not contain volatile solvents and with respect to chemical composition not dangerous.

After the application of LCV protein stains like Amido Black and Acid Violet 17 can still be used. Apparently, LCV can also be used after luminol [1], however it first needs fixing with 2% sulfosalicylic acid otherwise leaching with loss of detail occurs.

Under the influence of light unreacted LCV can still be oxidised causing background coloration. This process is however very slow so there is plenty of time to photographically record visualized marks.

Crystal violet is known [2] to fluoresce in the deep-red and infrared after oxidation (especially at low concentrations.) This might yield additional marks or make it possible to enhance developled marks.

Shelf life

Once solution A and B are mixed the shelf life when stored in the dark and cold (refrigerator) is several months. To maximize shelf life BVDA ships the reagent as two separate solutions, one of which contains the hydrogen peroxide. This extends the shelf life appreciably although an exact time is hard to name. It might also depend on the particular batch of LCV and/or other small variations in the chemicals used. On standing the LCV solution slowly darkens. When the surface already becomes purple when there is no blood present, the reagent should obviously be discarted. The hydrogen peroxide solution also slowly decomposes.

Therefore, we strongly recommend to store the reagent in the refrigerator.

History

LCV was conceived and over the course of several years improved by John F. Fischer, who worked for the Orange County Sheriff's Office in Orlando (Florida). The FBI lab in Washington started using it at the end of 1993.
In June 1994 John Fisher gave a presentation on LCV at the FBI academy in Quantico (International Symposium on Footwear and Tire Tread Impression Evidence). Bill Bodziak who at the time still worked for the FBI gave a lecture on it at the first SPTM-conference (the working group later became part of ENFSI) in Helsinki (Finland), May 1995 [1].
In 1996 Bill Bodziak published an article on LCV in the journal Forensic Science International [3].

Footnotes

[1]  Handout of a lecture by Bill Bodziak: "The use of Leuco Crystal Violet to enhance shoe prints in blood", Shoe Print/Tool Mark Examiners (SPTM) conference, May 1995, Helsinki (Finland).
[2] Bramble, K.; Cantu, A.A.; Ramotowski, R.R.; Brennan, J.S., "Deep Red to Near Infrared (NIR) Fluorescence of Gentian Violet-treated Latent Prints", Journal of Forensic Identification 2000, Vol. 50, no. 1, pp. 33-49.
Also see the letter by Menzel, E.  Journal of Forensic Identification 2000, Vol. 50, No. 3, pp. 245-249.
[3]  Bodziak, William J. "Use of leuco crystal violet to enhance shoeprints in blood", Forens. Sci. Int., 1996, Vol. 82, pp. 45-52, [doi:10.1016/0379-0738(96)01965-2]