G. Stewart Walker

The analysis of dyes in ball point pen inks on single paper fibres using laser desorption ionisation time of flight mass spectrometry (LDI-TOFMS)

An important requisite for the forensic analysis of inks on documents is that damage to the document is avoided or minimised. This paper describes a technique for dye identification in ballpoint pen inks using LDI-TOFMS on single ink bearing paper fibres and its application to a case. A single ink bearing paper fibre can be prised from the surface of the document under a stereo microscope and presented to the instrument for analysis without further treatment. This sampling process causes imperceptible damage to the surface of the document. Clear mass spectrometric identification of the ink dyes is obtained. A case example is provided to illustrate the practical application of the technique.

Application of liquid chromatography-tandem mass spectrometry to the analysis of benzodiazepines in blood

A sensitive and selective high-performance liquid chromatography/atmospheric pressure chemical ionisation tandem mass spectrometry (HPLC/APCI-MS/MS) method for the simultaneous detection of 18 benzodiazepines and metabolites in human blood is described. The procedure utilises butyl chloride extraction at alkaline pH followed by reversed-phase liquid chromatography. The technique is suitable for screening analyses and confirmation of identity of the benzodiazepines at their lowest reported therapeutic concentrations using 500 μL of blood. The method has been successfully applied in forensic cases involving low concentrations of benzodiazepines.

Stability of Serotonin-Selective Antidepressants in Sterile and Decomposing Liver Tissue, †‡

It is well established that bacteria are capable of degrading selected drugs during decomposition. The aim of this study was to investigate the stability of several serotonin‐selective reuptake inhibitor antidepressants and venlafaxine during putrefaction in porcine liver macerate inoculated with porcine cecal contents rich in bacteria. Blank liver matrices, sterile liver macerates, and sterile aqueous controls were included with the experiment performed for 57 days at 20°C under anaerobic conditions. A liquid chromatography/mass spectrometry method was developed for quantitative determination of the drugs investigated in both sterile and decomposed liver matrices. The method was found to encounter matrix effects not detected during the validation stage. Citalopram, paroxetine, sertraline, venlafaxine, and fluoxetine were found to be stable under the experimental conditions; however, fluvoxamine was found to be decreased by c. 50% over 57 days in bacterially inoculated liver macerate. This study suggests that fluvoxamine concentrations in cases with evidence of decomposition/putrefaction should be interpreted with extra caution.

Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) - Part 2: Forensic inter-laboratory trial: Bulk carbon and nitrogen stable isotopes in a range of chemical compounds (Australia and New Zealand)

Abstract:  Comparability of data over time and between laboratories is a key issue for consideration in the development of global databases, and more broadly for quality assurance in general. One mechanism that can be utilized for evaluating traceability is an inter‐laboratory trial. This paper addresses an inter‐laboratory trial conducted across a number of Australian and New Zealand isotope ratio mass spectrometry (IRMS) laboratories. The main objective of this trial was to determine whether IRMS laboratories in these countries would record comparable values for the distributed samples. Four carbon containing and four nitrogen containing compounds were distributed to seven laboratories in Australia and one in New Zealand. The laboratories were requested to analyze the samples using their standard procedures. The data from each laboratory was evaluated collectively using International Standard ISO 13528 (Statistical methods for use in proficiency testing by inter‐laboratory comparisons). “Warning signals” were raised against one participant in this trial. “Action signals” requiring corrective action were raised against four participants. These participants reviewed the data and possible sources for the discrepancies. This inter‐laboratory trial was successful in providing an initial snapshot of the potential for traceability between the participating laboratories. The statistical methods described in this article could be used as a model for others needing to evaluate stable isotope results derived from multiple laboratories, e.g., inter‐laboratory trials/proficiency testing. Ongoing trials will be conducted to improve traceability across the Australian and New Zealand IRMS community.

An Investigation into the Spatial Elemental Distribution Within a Pane of Glass by Time of Flight Secondary Ion Mass Spectrometry

Abstract:  Advances in the technology employed for the manufacture of glass have resulted in a final glass product with little variability in terms of its physical and optical properties. For example, the refractive index of Australian float glass tends to lie between 1.5189 and 1.5194. It has therefore become necessary to complement physical and optical methods for forensic glass comparison with instrumental elemental analyses. In a previous study, time‐of‐flight secondary ion mass spectrometry has been shown to offer potential for the analysis of glass particles as small as a few tens of microns across. In this study, the three‐dimensional homogeneity of a sheet of float glass is described, and consequences for forensic elemental analysis of glass particles of such size are explored. Variation in Si, Ca, Mg, and Na levels immediately under the nonfloat surface was observed, with the variance accompanied by a decrease in refractive index.

Re-oxygenation of post-mortem lividity by passive diffusion through the skin at low temperature

Post-mortem hypostasis develops due to passive settling of the blood under the effect of gravity after death. Due to consumption of oxygen in the tissues by residual cellular activity after the circulation has stopped, lividity is composed of deoxygenated blood. It has been previously shown that cooling of a body causes lividity to oxygenate, changing from a dark red/blue to a pink/red color, due to hemoglobin’s increased affinity for oxygen at low temperature. This study has confirmed that this occurs by passive diffusion through the skin, but that this can only occur within a limited time frame. The reasons for this process and its potential forensic application require further investigation.

Rapid Screening for the Detection and Differentiation of Gamma-Hydroxybutyrate using Ion Chromatography

Abstract:  The analysis of gamma‐hydroxybutyric acid (GHB) is problematic because it is hygroscopic, it lacks a good UV chromophore, and it undergoes heat‐induced cyclization. This paper presents a new method utilizing ion‐exchange chromatography (IC) with conductivity detection. The simple sample preparation, rapid analysis time, and inorganic anion detection capabilities are all advantages over the current methods. The detection of inorganic salts (formed during GHB synthesis) gives insight into the synthetic route utilized and can aid in drug seizure comparison. The developed method has a detection limit for GHB anions of 0.57 mg/L and chloride of 0.22 mg/L. A comparison of this technique with a current gas chromatography–mass spectrometry technique is presented, and a t‐test found that the two methods’ results are not statistically different at the 99.9% confidence level demonstrating the merits of this fast, simple, and informative IC method as a routine screening tool.

Analysis of Soils in a Forensic Context:Comparison of Some Current and Future Options

The increasing number of sophisticated techniques available for application to forensic, environmental, and forensic environmental investigations raises questions about their relative discriminating power, and the relative cost and return. A number of different variables including ease of use, availability, relative cost and admissibility in court should be considered to determine a hierarchy of techniques for aiding selection by investigating authorities. Of recently developed techniques, confocal RAMAN, laser induced breakdown spectrometry (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) are considered for their potential for cost effective discrimination of soils. Outcomes of comparisons between techniques suggest that a hierarchy of techniques can be developed, which may change with each case depending on the resources available and the needs of the investigation.

Investigation into the potential for post-mortem formation of carboxyhemoglobin in bodies retrieved from fires

The forensic investigation of a deceased person retrieved following a fire includes measuring carboxyhemoglobin. A carboxyhemoglobin saturation above 10% is considered indicative of respiration during a fire, implying the person had been alive. This relies on the assumption that carbon monoxide will not diffuse into blood used for toxicological analysis. This project investigated the potential for carbon monoxide to passively diffuse into a body and if carboxyhemoglobin levels could become elevated post-mortem. Stillborn piglets with intact skin were exposed to carbon monoxide. Carboxyhemoglobin formed in the hypostasis of the skin, but carboxyhemoglobin levels in blood from the heart and chest cavities were not significantly elevated. However, defects in the skin over body cavities (producing breaches to replicate cases with stab wounds or heat damage) resulted in cavity blood carboxyhemoglobin levels above 10%. A review of fire death cases in South Australia 2000–2015 was performed to determine the origin of the blood samples used for toxicological analysis and the incidence of cases with breaches of body cavities. This revealed a small number of cases in which blood from the cavities had been analyzed when cavity breaches were present. Thus, there is a potential for significant elevation of carboxyhemoglobin saturation post-mortem in forensic casework involving bodies retrieved from fires.