Lim Chin Chin
ASEAN Virtual CoE Technical Workshop organised by DSO National Laboratories
Forensic evidence can be found in trace and bulk amounts in all the three states: volatiles, liquids and
solids. They can be natural or man-made, homogeneous or heterogeneous. The nature of their matrices
can be simple or complex, clean or dirty, with the target analyte present in distilled water versus dirty and unknown burnt material. Common forensic evidence include fibres, paint fragments, explosives, ignitable liquids, household or industrial chemicals, hazardous or toxic chemicals, illicit or counterfeit drugs, bloodstains, body fluids and DNA.
For the essence of forensic evidence to be distilled and effectively used, the relevant items must be
correctly sampled and their integrity preserved throughout the forensic process: from the scene to the
courtroom. Authorised persons handling or processing the evidence need to use the right tools,
equipment, methods and storage conditions to ensure that results obtained are representative,
scientifically reliable and able to withstand court scrutiny. Control samples and known samples may need to be collected, analysed and compared with the questioned samples to determine the background and distinctiveness of the evidence.
The intriguing nature of forensic evidence makes it challenging at times to decide on a sampling strategy,
sampling plan and sampling protocol to collect the evidence, analyse and interpret it. Sampling cannot be performed in an arbitrary or one-size-fits-all manner. Sampling must be optimised, taking into
consideration different physical and chemical properties, reactivity, stability, toxicity, degradation, as well as analytical methods appropriate to the evidence.
This presentation will outline the What, Where and How of sampling various types of forensic samples.
The case studies shared will enhance your understanding of the factors to consider when selecting a
sampling plan and establishing sampling protocols at different stages of the forensic process.