Physical Evidence in Drug Intelligence, Part 2: Discrimination of Packaging Tapes by Colour: discrimination of packaging tapes by colour

The authors have considered routine exploitation of physical evidence from seized shipments of illicit drugs for intelligence purposes. Part 1 of this series addressed the identification of polymer type within the adhesive of packaging tapes and raised important issues with regard to how data should be collated in a database as a basis for reliable drug intelligence. This article expands on this topic by addressing the use of colour for achieving the same aim. By using a relatively simple instrumental technique to analyse opaque ‘brown’ packaging tapes, it was found that colour was an effective way to discriminate between different adhesive tape samples. However, initial results showed that the analysis of colour in packaging tapes was more complex than assigning semisubjective names to particular hues (e.g. light brown, green brown, etc.). Instead, samples in the population often differed only slightly from one another and hence proved difficult to categorise. Thus, a database or analyst must avoid using such ‘discrete’ labels and instead make use of ‘continuous’ numerical data. Here, CIELab chromaticity coordinates were used to define representative colour spaces for each tape sample and these were then compared to determine whether two such volumes intersected. This process would decide whether or not the samples could be discriminated. While several sets of data were compared, further work needs to be carried out into the consistency of colour within single rolls of tape or batches of tape.