Differences in duration and intensity of chemiluminescence between blood and other reactive substances when screening with luminol
OA Version
Citation
Abstract
After crimes where there has been a lot of bloodshed, it is important for crime scene investigators to be able to locate latent, or hidden, bloodstains so that they can visualize bloodstain patterns and collect stains for further testing. Bloodstain patterns can help to identify the events of a crime scene, aid in determining manner of death and reconstruct a violent crime scene for presentation in court. Blood evidence from a crime scene is also important for obtaining a DNA profile. These analyses can be impeded by the obliteration of bloodstain pattern evidence, either intentionally or by the environment.One of the most common blood enhancement reagents, or chemicals, for crime scene use is luminol. Luminol is a presumptive test used to enhance the visibility of faint or non-visible bloodstains through a chemiluminescent reaction. Luminol is sensitive to light (and therefore must be used in the dark), has a short shelf-life and is hazardous. Luminol produces a chemiluminescence in the presence of hemoglobin, a component of blood, which catalyzes the oxidation of luminol. While luminol can be sensitive to blood up to a 1:100,000 dilution, it is not very specific, and has been found to react in the presence of some other body fluids, plant juices, cleaning products, enamel paint and rust.
The purpose of this study was to test a variety of substances that have been found to react with luminol and compare the duration and intensity of these reactions to those of undiluted and diluted blood. The study found that enamel paint, bleach-containing products and another non-bleach cleaner can react with luminol. Additionally, saliva and urineĀ¬, depending on the donor, and rust reacted but were not detected by the camera. None of the plant juices tested in this study reacted with the luminol.
Further, it was determined that blood luminesced brighter than other reactive substances overall when treated with luminol. However, at certain time points, bleach-containing substances luminesced brighter and/or longer than undiluted and diluted blood, or the reactions were so similar in these respects that they could not be distinguished. Results from this study also supported the commonly held belief that older bloodstains produce a stronger reaction with luminol.
While the lack of specificity of luminol can complicate conclusions regarding the presence of blood at a crime scene, many of the substances tested in this study produced a visually distinct reaction from blood and from each other, which can aid in crime scene investigations that may involve blood.
Description
2024