The chemistry section provides a forensic chemistry service to the state of South Australia, primarily for matters being investigated by South Australian Police (SAPOL) and prosecuted by the Office of the Director of Public Prosecutions.
Other clients of the chemistry section may include SA Health, Australian Customs Service, Australian Federal Police, Australian Defence Force and a number of non-government clients.
The chemistry section comprises three distinct forensic disciplines that each provides a range of analytical services: illicit drugs, trace evidence and document examination.
Video: working in forensic chemistry
The illicit drug group performs analyses on suspected illicit drug exhibits and attend, process and analyse samples from clandestine drug laboratories encountered across South Australia. Illicit drug examinations determine the presence and quantity of illicit drugs present in exhibits. The illicit drugs commonly identified in South Australia include:
- 3,4-methylenedioxymethylamphetamine (MDMA)
- 'new psychoactive substances' eg synthetic cannabinoids, cathinones and other amphetamine-type drugs.
Botanical examination is conducted by specially trained analysts in the examination of plant material suspected of being cannabis and expert opinion is provided relating to sites growing cannabis, known as 'crops'.
A clandestine drug laboratory (clan lab) is a site involved with the manufacturing of illicit drugs. Clan labs in SA are located in residential, rural or commercial properties. A specially trained chemist will attend the scene and provide scientific advice to SAPOL during the assessment and processing phases to minimise hazards associated with processing.
Chemicals are categorised and sampled for further analysis in the laboratory. The results of analysis determine what drug was being manufactured, how it was made and how much illicit drug could have been made.
The illicit drug section works closely with clients providing reports on illicit drug trends, including issuing alerts to these agencies about detections of illicit drugs that pose an increased acute health risk for users.
The trace evidence group involves the examination, and comparison or identification of non-biological trace evidence from a crime scene, vehicle collision, suspect, or victim such as:
- gunshot residue (GSR)
- ignitable liquid residues (ILR)
- miscellaneous chemical eg personal defence sprays (PDS), vehicle light filament examinations and tyre examinations.
The analysis uses a variety of analytical techniques examining the physical, optical and chemical properties of the material. Trace evidence is usually based on either comparison, or identification.
Comparison involves comparing a 'foreign' exhibit with a 'known' or 'putative' source, eg comparing glass fragments from the clothing of a road crash pedestrian with glass from a suspect’s vehicle, or comparing paint smears on a screwdriver with window-frame paint from the point-of-entry of a break-in.
Identification is the generic, or class, identification of evidence. For example analysis of debris from a fire scene may identify the presence of petrol, or the analysis of samples taken from the hands of a suspect of a drive-by shooting may identify the presence of GSR.
Glass analysis compares the physical and optical properties (and, at times, the elemental composition) of known and questioned glass exhibits. As recovered glass fragments are generally too small for direct comparison of physical measurements, comparison is made using an automated system specifically designed for this purpose.
Microscopic examination for colour, texture and layer structure, micro-analysis to determine the organic composition, ultra-violet (UV) & visible microspectrophotometry to compare colours and UV inhibitors, and scanning electron microscopy to determine the inorganic composition.
Gunshot residue (GSR)
GSR is deposited on the hands by activities such as firing a weapon, being in close proximity to a discharging firearm, or coming into contact with an object or surface that is contaminated with GSR. A scanning electron microscope with an energy dispersive X-ray detection system (SEM-EDS) coupled with an automated search facility is used to identify the morphology and elemental composition of any particles found.
Ignitable liquid residue (ILR)
Identification of the presence of a volatile chemical, often in fire debris, to determine whether an accelerant has been used to assist in starting the fire. Volatiles are analysed by removing a headspace (or 'surrounding air') sample of an exhibit, and then analysing that sample by means of a gas chromatograph/mass spectrometer.
Identification of pre or post-blast residues or substances, and may include commercial, military or improvised explosives or devices.
Identification of fabrics, carpets, and ropes commence with microscopic comparisons where fibres are viewed side-by-side on a comparison microscope. Further examinations may include microchemical/microsolubility testing, colour comparisons via microspectrophotometry, fibre cross-section determinations, and chemical composition comparisons via infrared spectrophotometry.
Physical or chemical analysis of unknown materials for identification or comparison purposes.There are numerous types of evidence which fall into this category. Some of the more common examples include:
- personal defence sprays
- adhesive tapes
- unknown liquids and powders.
The document examination group predominantly undertakes handwriting and signature comparisons to determine their authorship. Other document examinations include determining whether a document has been altered from the examination of ink, evidence of erasures, obliterated entries or page substitutions. Valuable evidence can be visualised from impressions on the surface of a page that may not be visible with the naked eye.
The general propositions of handwriting examinations, which enable handwriting to be a useful form of ‘opinion identification evidence’ in the forensic sciences are:
- No two persons write exactly the same: no two skilled writers have been reported that exhibit identical handwriting characteristics on extended writings (inter-writer variability).
- No one person writes exactly the same way twice: the natural handwriting of individuals varies.
- Individuals have difficulty copying the handwriting characteristics of others accurately.
- Individuals find it difficult to disguise their handwriting characteristics on extended writings.