Fluorescent Gentian Violet

(The following article is reprinted from the Oct./Dec. 1995 issue of the Texas Division I.A.I. newsletter)

Physical Evidence Section
Dallas County Sheriff's Dept,

Gentian violet (crystal violet) is a dye that produces a purple colored image when reacting to fatty constituents of sebaceous sweat1.  It has been very effective for the development of latent prints on the adhesive side of various types of tape.  As with all types of chemical process for developing latent prints, to date, the forensic examination of items such as hair, fibers, handwriting, blood, or other body fluids must be considered prior to any item of evidence being chemically treated.  Since fluorescent gentian violet (FGV) is comprised of gentian violet and rhodamine 6--G, forensic examination of any evidence should be evaluated prior to the use of fluorescent gentian violet (FGV).

The application technique used by this Department on the adhesive side of black electrical tape with crystal violet was developed by one of its members, G.W. Tucker2 .

Modified mixing instructions for FGV:

Stock solution
Crystal Violet 1.5 grams
Ethyl Alcohol 100 ml

Working solution
Stock solution 10 ml
Distilled water 500 ml
Rhodamine 6--G .5 grams

Modified application procedure for FGV:

1. Apply working solution directly onto the adhesive side of tape (time of exposure may vary... 10 seconds or longer), using either below listed application.

a. Application using a camel
hair brush
b. Application using bath

2. Rinse excess from tape using a gentle flow of tap water.

3. Dry tape with a hot hair dryer (allowing to air dry creates water bubbles that can interfere with laser examination of latent print).

4. Examine under Laser.

5. Photograph any visible latent prints.

The purpose of this experiment was to enhance the comparable quality of a latent print (s) developed on the adhesive side of black electrical tape, and to preserve the latent print(s) through laser photography developed by this Department3.  Very positive test results have been obtained on the adhesive side of black electrical tape using the fluorescent gentian violet. However, black electrical tape is not the only type of tape used in these experiments. Positive test results have also been obtained on tapes such as grey duct tape, transparent tape, and paper adhesive labels.  The test results using this application on items such as gummed labels or envelopes have thus far been negative.

It has been found that an excessive amount of rhodamine 6--G powder will leave a prominent dark red residue on the evidence.

The experiment was conducted using the Department's Spectra--Physics Model 164--09, 5 watt Argon Ion Laser with the remote power source setting the laser power at 10 (full power).

1. Science Research and Development Branch, Home Office.  Manual of Fingerprint Development Techniques (Abridged). 1988:55.

2. G.W. Tucker: A Modified Crystal Violet Application Technique for Black Electrical Tape.  J.F.I. 1990;40:148--150.

3. J.G. Cron: Laser Photography with Polaroid Film.  Identification News. 1984:5.

This article was reprinted in �THE PRINT�
Volume 12(4), July/August 1996, pg 10
and has been obtained from the online library provided by the

Southern California Association of Fingerprint Officers