Chow Y.S*, Lee L.K., Lim Chin Chin, Michael Tay Ming Kiong
5th European Academy of Forensic Science conference
Glasgow, United Kingdom, 9 Sep 2009, CS06 (poster presentation)
The aim of this paper is to investigate the ability of two commercial test kits to detect bloodstains which are chemically treated. Chemical agents include cleaning agents and chemical enhancement agents.
Cleaning agents are commonly used 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 exhibited greater sensitivity and ease of use compared to RSIDTM blood kit. It 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. It was difficult to detect chemically treated blood on wood, the most porous substrate used.
From this study, Amido Black is the preferred chemical enhancement agent for faint blood stains because it has minimal interference with the two commercial blood test kits. The HEXAGON OBTI kit was more sensitive and had greater versatility in detecting blood treated with different enhancement agents and on different substrates. However, unlike the RSIDTM blood kit, it is not specific to human blood.