Lee L.K*, Chow Y.S, Lim Chin Chin, Michael Tay Ming Kiong
AFSN, KL, Malaysia, Nov 2009 (oral presentation)
The aim of this paper is to investigate the specificity, sensitivity and the ability of two commercial test kits,“HEXAGON OBTI” and “RSIDTM blood, to detect human bloodstains and bloodstains which are chemically treated. Chemical agents include cleaning agents and chemical enhancement agents (with/without fixing agents).
The identification of human blood at the crime scene using a fast and reliable technique is important for investigative purposes. Human bloodstains, human body fluids (saliva, urine, semen) and animal bloodstains (sheep, cow, fish, pig, chicken, dog, goose, goat, cat, macaw, buffalo and eight kinds of higher primates) were used for this study.
Cleaning agents are commonly used by criminals to remove blood evidence at crime scenes. Chemical enhancement agents are also used at scenes to enhance faint bloodstains, marks and prints for pattern identification. Hence, it is necessary and useful to investigate if the detectability of blood by common commercial blood test kits is affected by the use of these chemical agents.
Two commercial blood confirmatory kits: “HEXAGON OBTI” and “RSIDTM blood, four blood enhancement agents, ten common household cleaning agents and eight different types of substrates were used in this study. The four enhancement agents tested were Amido Black, Leuco Crystal Violet, Luminol and Ninhydrin. Neat and diluted blood stains (10x and 100x dilutions) were deposited on the substrates to investigate substrate effects.
The HEXAGON OBTI kit was able to detect blood treated with all the different types of cleaning agents and enhancement agents. On the other hand, the RSIDTM kit was unable to detect blood stained with bleach and hydrogen peroxide. Amido black appeared not to interfere with the functioning of both test kits. It appeared to be the preferred chemical enhancement agent for enhancing bloodstains, followed by Ninhydrin. Most treated stains gave better results when no fixing agent was applied.
The HEXAGON OBTI kit exhibited greater sensitivity and ease of use compared to RSIDTM blood kit. However, its main drawback is its non-specificity to human and higher primate blood, compared to the RSIDTM blood kit.