Luminol is used widely in forensic science by crime scene investigators. Luminol is used to presumptively test if blood is present on a surface. Most crimes scenes are violent and hence blood is mainly found in crime scenes. Blood in a crime scene can be dried or even wiped out using a clothing hence is not visible to the eye. Luminol reagent enhances non-visible blood stains in crime scenes and materials left at a crime scene (Larkin and Gannicliffe 71). Luminol is one of the most used blood detection reagents due to its sensitivity. Luminol is a chemical that turns into a green hue of blue when it is introduced on a surface with blood. Luminol emits light in a blood reaction through chemiluminescence (Radi et al. 51). Chemiluminescence is when light is emitted in a chemical reaction. Luminol reacts with hemoglobin which is found in blood hence producing a greenish glow. Luminol is preferred in crime scene science because it is very sensitive even to minute amount of blood. Surfaces which are suspected to contain blood are sprayed with a luminol solution, and on contact, the hemoglobin in the blood reacts with the luminol. A crime scene officer can then photograph the reaction so as to document the evidence. Blood in crime scenes are exposed to different varying temperatures and conditions. They can even undergo some degradation like normal body fluids. Variation in temperatures and degradation does not reduce the efficiency of luminol (Quickenden, Ennis, and Creamer 276). In a crime scene, any small trace of evidence left behind is vital to the case. A small trace of blood can stick to a surface for many years without being noticed. Luminol is useful in identifying surfaces with blood. The surfaces include floors or even car seats. Luminol is a presumptive test to test is blood is present since certain chemicals will also glow when they react with luminol as if they were blood. More tests such as DNA tests are done to prove the evidence to be blood. The presence of blood in crime scene does not always solve the crime on its own, but it leads investigators to investigate the correct theories. Luminol can be used to identify the blood spatter pattern in a crime scene which can be useful in determining the kind of weapon that may have been used in committing the offense.
Luminol is more sensitive than other presumptive tests of blood such as the use of phenolphthalein. However, despite the fact that luminol has high sensitivity, it is not highly used in all cases because of concerns about its toxic nature (Larkin and Gannicliffe 71). Luminol causes irritation of soft membranes in the eyes and the nasal cavity. Some studies even suggest that luminol may be a mutagen playing a role in causing certain cancers. The use of luminol is not limited to criminal science (Dilbeck 706). In early years, it was used to stop bleeding since it promotes blood clotting. The health effects of luminol have not been validated hence it is still used in crime scenes. Studies have found out that 3-aminophthalhydrazide, a chemical used to synthesise luminol is not carcinogenic though it may lead to irritation and burns when it comes into contact with the body. Presumptive blood tests have been known to produce false tests hence all of them are presumptive (Nilsson 2). Luminol, however, is more sensitive than all the other reagents used in the presumptive tests for blood. Luminol also does not interfere with the blood evidence since it does not decompose the DNA materials in the blood. When determining if the material is indeed blood, serological tests need to be done. Luminol does not impede the chemicals being used in serological tests to determine if the blood is from a human or animal.
After the blood has been identified, the sample is collected and PCR techniques used to extract DNA from the blood. The use of luminol does not interfere with the further methods to be used for the identification of blood such as PCR and tandem repeats typing (Nilsson 7). Prolonged exposure of the blood to luminol may degrade the DNA in the blood evidence hence it should not be used in a long period of time. If used well, luminol can be very useful to a crime scene. Luminol is often used to envisage blood that may have not been or seen by use of other methods. In a fictional case, a woman was kidnapped from her home, but there was no evidence of a struggle. However, you notice a place which looks cleaner than other areas, like it was cleaned (Ribaux et al. 67). Luminol will be used to determine if there are traces of blood in the spot. Glowing spots is an indication that blood may be there. Glowing areas are photographed as evidence (Grispino 29). Patterns can be identified if they glow under luminol. Luminol is important in the presumptive test of blood. However, it is not used to confirm the presence of blood, and further tests have to be done. Luminol is often used when the blood stains are not visible. Luminol has an advantage over other presumptive tests as it is cheap and does not interfere with further confirmatory tests. Luminol, however, can produce false positives if it comes into contact with chemicals like cleaning bleach. Also, it is possible that it may be carcinogenic. Luminol emits light when it comes into contact with blood. Its adoption has been increasing since it can be used to identify stains that have been there for long and cannot be seen by the naked eye.
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Grispino, RRJ. “Luminol and the Crime Scene.” Prosecutor 25.1 (1991): 28–32. Print.
Larkin, Tony, and Chris Gannicliffe. “Illuminating the Health and Safety of Luminol.” Science and Justice 48.2 (2008): 71–75. Web.
Nilsson, Anders. “The Forensic Luminol Test for Blood: Unwanted Interference and the Effect on Subsequent Analysis.” Link?ping University Faculty of Health Sciences Project Microbial Biotechnology (2006): n. pag. Print.
Quickenden, T. I., C. P. Ennis, and J. I. Creamer. “The Forensic Use of Luminol Chemiluminescence to Detect Traces of Blood inside Motor Vehicles.” Luminescence 19.5 (2004): 271–277. Web.
Radi, R. et al. “Peroxynitrite-Induced Luminol Chemiluminescence.” The Biochemical Journal 290 ( Pt 1 (1993): 51–57. Print.
Ribaux, Olivier et al. “Intelligence-Led Crime Scene Processing. Part II: Intelligence and Crime Scene Examination.” Forensic Science International 199.1–3 (2010): 63–71. Web.