Chow Y.S*, Koh C.W, Oh S.P., Lim S.M., Yew S.Y., Lim Chin Chin
6th European Academy of Forensic Science Conference,
20-24 Aug 2012, The Hague, Netherlands (Poster Presentation)
In Singapore, the common packaging materials used in drug trafficking are plastic bags, adhesive tapes and plastic drinking straws. The characteristics of plastic bags and adhesive tapes have been studied and are well documented in forensic literature and databases. These two types of packaging materials have proven to be very useful in providing linkages between the drug traffickers and the individuals consuming the drugs.
Unlike plastic bags and adhesive tapes, the evidential value of straws is relatively unknown. To our knowledge, there is currently no forensic literature on the possible characteristics of straws that could be used for associative purpose.
The objective of this paper is to determine the significance and usefulness of straws as forensic evidence. In this study, over eighty packets of visually similar straws were purchased from different commercial outlets in Singapore and examined.
A range of physical characteristics, such as polarizing light patterns, thickness, circumference, weight per unit length and melting point were examined to assess their potential for discriminating straws from different packets and from different sources. Thickness, circumference and weight per unit length measurements resulted in discriminations of approximately 25%, 58% and 60%, respectively. Melting point, as determined using a melting point apparatus, was found to be not useful and subsequently discontinued.
The straws examined could be classified into several groups based on polarising patterns and this yielded a discrimination of approximately 67%. Finally, the manufacturing marks on the straws were examined using comparison microscopy. This was found to be the most discriminating technique, with a discrimination of about 93% even among straws with similar polarising patterns. The straws which could not be discriminated using comparison microscopy were from packets that had been purchased from the same commercial outlet, mostly on the same day and up to a maximum of one week. It is highly plausible that the packets of straws which could not be discriminated using manufacturing marks had been manufactured by the same machine within a period of time whereby the physical characteristics and manufacturing marks remained relatively similar. Crucially, all straws that had been purchased from different commercial outlets were discriminated using this technique. Some successful cases using the above techniques will be shared in this presentation.
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