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Lueco Crystal Violet: (The following article is reprinted from the Oct/Dec 1995 issue of the Arizona Identification Council publication)
by ROBERT A. MILLER JR. Abstract. Serological reagents for presumptive blood testing that have been utilized for blood detection and development have become beneficial to the latent print examiner. Due to the sensitivity and specificity of these reagents, they have been used to develop invisible or faint blood impression evidence. Lueco crystal violet (LCV) is a safe, simple and effective reagent for blood enhancement and development on virtually all types of surfaces. Introduction Specialized techniques are often necessary to successfully develop and preserve blood impressions. Bloody fingerprints and shoe prints are often deposited at crime scenes and on evidence. These often present quite damning evidence. Blood impressions frequently need enhancing to be photographically recorded. Serological reagents and general protein stains have been widely used as enhancement techniques. Certain chemical reagents react with the heme moiety of the hemoglobin molecule of the red blood cells in blood. Heme will catalyze an oxidation reaction and convert the reagent to an oxidized product that is colored [1]. These reagents have varied from benzidine preparations to o--tolidine and diaminobenzidine (DAB) [2]. The lueco crystal violet (LCV) reagent is a catalytic test for blood [3]. LCV is the colorless form of a common latent development reagent crystal violet. The oxidized reaction of LCV is a dark violet color. The reaction is specific for blood, as opposed to protein stains such as amido black, that tend to give a high background coloration on porous surfaces or where proteinaceous substrates are present. LCV produces little background coloration and no destaining is necessary. Unlike DAB, it is a simple, efficient, one--step technique that is extremely safe to prepare. Material And Methods Lueco Crystal Violet (LCV) [4]
10 grams 5-- Sulfasalicylic Acid (2%) Dissolve 5-- Sulfasalicylic Acid into Hydrogen Peroxide. Add leuco crystal violet while stirring vigorously with a magnetic stirrer. Leuco crystal violet will remain stable for several months when stored in an amber bottle and at room temperature. Storage in a refrigerator can extend the reactivity of LCV [4]. LCV is air and light sensitive. In the dry state, it must be stored under nitrogen. Serological examinations should be conducted prior to treatment with LCV. LCV should only be applied to thoroughly dried blood impressions. Application of LCV is conducted with a wash bottle or dropper. Excess LCV reagent may cause diffusion of the blood impression. This can be prevented by evacuating or absorbing the LCV reagent from the impression after it has been developed, usually within 30 seconds. A dark violet impression will continue to develop. Exposure to intense light may cause the background to become violet due to photoionization of the LCV [4]. Therefore, the impression should be photographed as soon as possible. After the impression has been photographed, further enhancement may be conducted. Amido Black, in both the methanol/acetic acid and aqueous formulations, often provides additional enhancement. Safety considerations should be exercised while using LCV. Lueco Crystal Violet can cause eye and skin irritation. 5-- Sulfasalicylic acid may be slightly irritating to the skin with discoloration and pain. The diluted solutions used with LCV will significantly reduce this effect. As with any chemical, safety considerations should be utilized during preparation and usage of LCV. Gloves, protective eyewear, laboratory coats, dust/mist respirators, and proper ventilation should be employed to limit contact with the reagent. Results LCV enhanced blood impressions are a dark, vivid, violet color and are fixed by the 5--Sulfasalicylic Acid. Due to the sensitivity of this reagents additional trace blood, that was not visible to the naked eyes will be developed. LCV is not only limited to bloody fingerprints, but to all impression/pattern blood. Conclusion
LCV provides a simple and efficient method for blood enhancement that can
be conducted both at the crime scene and the laboratory. It provides a
safe reagent for effectively enhancing blood impression on most surfaces
without staining the background.
For further information contact:
Robert A. Miller Jr C.L.P.E. (602) 261--8102 References 1. Lees H.C. and Gaensslens R.E., Advances in Fingerprint Technology. Elseviers 1991, pp.83--87. 2. Sahss P T DAB. “Advancement in Blood Print Detection,” Journal of Forensic Identification, 42(5)s pp. 412--420. 3. Gaensslens R.E., Sourcebook in Forensic Serology, Immunology and Biochemistry. Washington D.C., U. S. Government Printing Office.
4. Fischer, J.F., personal communications March23, 1995.
(Editor --— When reviewing this article with our Chemical Processing guru,
Criminalist Karla Taylor, she agreed that eliminating the need to “fix
the blood,” as in amido black processing, is a plus. She also indicated
that this procedure should work on painted surfaces where amido black,
with its methanol, frequently has problems.
This article was reprinted in “THE PRINT” |