Performance evaluation of activated carbon cloth for fire debris analysis with artificial neural network approach

Forensic fire investigates the origin and cause of the fire. Detection and identification of ignitable liquid (IL) residue in fire debris may provide the vital clue of the fire cause, especially important to prove incendiary fires. The scope of this study is narrowed to the usage of activated carbon cloth (ACC) as the adsorbent material by passive headspace diffusion as the extraction technique of IL residue. This study investigates the detection of selected target compounds that represent wide IL residue range from the lightest compound of n-hexane (C6) to the heavier compound of eicosane (C20) at different extraction parameters especially the temperature setting (60 °C to 120 °C) and exposure period (2 hours to 24 hours). Data sets from the chromatographic pattern vary significantly with different parameters were chosen. Computational modelling of artificial neural network (ANN) based on the pattern was developed and utilised to evaluate the extraction performance of ACC for optimisation purposed. The resolution of chromatographic behaviour of 14 selected target compounds that represent the ignitable liquid was used as input for the ANN model. The ANN display a response model of (2:2-17-14:14) allows the optimum condition with the practical setting to be 4 hours at 100 °C for urgent sampling while 18 hours at 80 °C is intended for overnight sampling. Selected optimum condition and practical settings for effective extraction of volatile compounds are important knowledge to facilitate busy laboratory operation as well as the identification and interpretation of complex fire debris samples. Thus, the finding of this research has a relevant implication for the forensic analyst who performed fire evidence investigation

Evaluation and Improvement of Capillary Microextraction of Volatiles Coupled to Gas Chromatography-Mass Spectrometry for the Analysis of Ignitable Liquid Residues in Fire Debris

A key aspect of fire debris analysis is the ability to extract the remnants of an ignitable liquid from a matrix with a high degree of reliability and sensitivity. Although there are several robust, standardized methods, there is no single technique universally applicable to casework. In this work a novel extraction technique – Capillary Microextraction of Volatiles (CMV) – has been applied, for the first time, for ignitable liquid residue (ILR) extraction. A 20-minute dynamic sampling laboratory protocol from traditional 1 L paint cans was established and optimized based upon ASTM guidelines. The development of new adsorption phases for CMV use are also reported. A phenyl-modified sol-gel phase demonstrated up to 8-fold higher recoveries of BTEX compounds from headspace sampling compared to previously reported CMV phases and four additional differently functionalized phases were synthesized and evaluated. Preliminary comparisons of the CMV to activated charcoal strips (ACS) and to solid-phase microextraction (SPME) demonstrated equivalent or slightly higher extraction efficiency relative to SPME, and over two orders of magnitude greater extraction efficiency relative to ACS. The versatility of the CMV has also been extended to portable analytical instrumentation. The device was successfully coupled to a TRIDION-9 portable GC-MS when combined with a needle trap, and both were evaluated for their applicability to fire debris analysis. The CMV/NTD technique demonstrated extraction capabilities similar to the CMV alone; however, ILR analysis by the T9 was heavily impacted by the limited chromatographic resolution resulting in complicated data interpretation. The CMV was similarly coupled to a Griffin G510 for dual evaluation. Also presented for the first time is a field ILR headspace sampling protocol involving the use of a paper drinking cup. A five-minute sampling/extraction protocol was sufficient to recover six key gasoline analytes from a 0.01 µL spike of gasoline with typical mass recoveries of 4 – 24 ng. An overall 21-minute analytical method was developed using the CMV/Cup protocol capable of detecting several ILR-associated compounds at up to 10x greater sensitivity than traditional extraction techniques. This body of work demonstrates the overall versatility of the CMV as applied to the entire field of fire debris analysis

The Recognition of Fires Originating from Photovoltaic (PV) Solar Systems

There has been an observable increase in the fitting of photovoltaic (PV) solar panels on the roofs of buildings in the UK over the last decade. The origin of some fires in domestic and commercial properties has been attributed to PV systems. This thesis examines the ability of fire examiners to recognise and record details of fires believed to have originated from PV systems, as well as investigating the effect of internal heating in direct current (DC) isolators to the point at which they fail. National fire data was examined along with the methods for collecting and collating these data. This clarified that national fire data cannot identify the specifics of electrical fires. Validity of these data was then tested by identifying the confidence and competence in the recognition of the origin of fire, (especially when associated with PV systems), of some fire staff responsible for collecting fire data. This suggests that some fire scenes examiners are not confident in their own ability to recognise fires originating from PV systems. Evidence for fires occurring in PV systems in Kent between 2009 and 2014 was then examined, including a cold case forensic review of the evidence. This provided an indication that a potential common point of failure, which may lead to fire originating from a PV system, was to be found within the DC section of the PV circuits and probably within the DC isolator switch itself. Experimentation revealed that internal heating of a terminal connection can lead to changes of the phase of the insulating material, causing failure of structural integrity and therefore allowing an arc to be established. Observable post fire indicators associated with this mechanism of failure have been identified as well as hydrocarbons evolved from pyrolysis of isolator insulating material. Finally, areas for further experimental research and training of fire staff are suggested as well as the modification of recording mechanisms and building regulations

Liquid Chromatography-tandem Mass Spectrometry of Fire Debris Evidence at Suspected Clandestine Methamphetamine Laboratories

The "One-Pot" methamphetamine production method involves the combination and use of highly reactive and flammable materials. Individuals attempting this method are creating clandestine laboratories within residences and other occupied structures, and the likelihood of a subsequent fire puts anyone nearby at risk. In the State of Oklahoma, if the production of methamphetamine causes a fire, the crime falls under the first degree arson statute, which can involve a prison sentence of 35 years, as opposed to 7 years for the production of drugs. The ability to detect methamphetamine and the One-Pot precursors in fire debris would strengthen the arson investigation. One-Pot methamphetamine reactions were carried out and the liquid and solid products were used to recreate a fire. Small burn cells were used to represent a residential environment. Several fire debris sample types were collected, including wall wipe samples, burned bottles, wood, and carpet. Each sample was analyzed for ignitable liquids using headspace extraction and gas chromatography-mass spectrometry (GC/MS). Following arson analysis, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to detect methamphetamine and pseudoephedrine, the methamphetamine precursor, in the fire debris. Additionally, fire debris samples were provided to local law enforcement and GC/MS was also able to detect methamphetamine in the fire debris. This work demonstrates that fire debris analysis can prove the presence of clandestine methamphetamine laboratories that result in arson fires.Forensic Science

A REVIEW OF CARBON DISULFIDE-GC/FID VERSUS THERMAL DESORPTION-GC/MS METHODS THROUGH THE LENS OF ANALYTICAL PROFICIENCY AND HUMAN AND ENVIRONMENTAL HEALTH RISK

NIOSH Method 2549 uses a hyphenated thermal desorption-gas chromatography/mass spectrometry instrumental method with thermal desorption tubes as the sample media for assessment of a variety of volatile and semi-volatile compounds. Other methods in the NIOSH Manual of Analytical Methods use solvent extraction methods for analysis. Of note are those methods that require the analysis of coconut charcoal tubes using carbon disulfide extraction and subsequent analysis via gas chromatography-flame ionization detector. Presented here is a comparison of the methodologies with regard to environmental and occupational health ramifications, as well as method sensitivity as evaluated via limits of detection and compound ranges. Evaluation of the changes of capability in thermal desorption instrumentation over the twenty years following the inception of the NIOSH 2549 Method call for a review of its use as a screening method. Advances suggest that quantitative methods are now appropriate based on said advances. Elimination of prior “one-shot” sample desorption that lead to the favor of solvent extraction for volatile organic compound analysis is no longer applicable. While both methods have certain limitations, benefits such as sensitivity gains related to pre-concentration (thermal desorption) techniques along with the added benefit of control via elimination of solvent support a review of standing methods for many volatile organic compounds in the NIOSH method lexicon. Drawing from updated reference methods and various studies, additional data can be gleaned to further support the advancement of thermal desorption as a trusted and versatile means of quantitation

The analysis and discrimination of pyrolysis products from biological and non-biological sources

This work involves the limited use of human tissue samples. These samples were obtained through body donation and under full ethical approval from the University of Strathclyde ethics committee. Products generated through pyrolysis of common materials can act as background compounds, interfering with the analysis and identification of potential human remains. The development of a robust methodology for the generation and analysis of volatile products from biological (porcine and human tissues) and non-biological (textile materials) sources stands at the core of this study, combined with examining various factors that causes these profiles to deviate. This process began with the validation of porcine samples as a substitute of human samples through the identification of similar key indicators, characteristic to both tissues. Interestingly, different temperature ranges (pre- and post-ignition) and type of porcine tissues utilised were found to effect the type of key indicators detected; and as such, has convincingly resolved key indicators reported in previous research literature. In addition, key indicators of pure and blended textiles were also established and the effects of blended fibres towards the overall thermal properties of the textile, highlighted. Alterations to the key indicators of individual porcine and textile samples were examined, subjectively and objectively, when both samples were burnt together (combined samples). Subjective analysis involved the scrutiny of the chromatographic output, revealing the dominance of key indicators of porcine samples over textiles for majority of the combined samples. EIC and EIP proved to be a beneficial tool in extracting key indicators of porcine samples in the presence of contamination (textiles). At 70% presence, SOFM provided an objective and successful classification and discrimination of pyrolytic data according to the type of pyrolysis product detected across textiles, porcine bones and also in the combined textile-bone samples while underlining meaningful associations amongst similar groups. Overall, although this work suggests that pyrolytic data can be unpredictable, such as its dependence on various factors, with suitable analytical and statistical techniques, it has revealed pertinent information on the key indicators of porcine, human and textiles samples and the inter- and intra-molecular changes that occur to them during pyrolysis.This work involves the limited use of human tissue samples. These samples were obtained through body donation and under full ethical approval from the University of Strathclyde ethics committee. Products generated through pyrolysis of common materials can act as background compounds, interfering with the analysis and identification of potential human remains. The development of a robust methodology for the generation and analysis of volatile products from biological (porcine and human tissues) and non-biological (textile materials) sources stands at the core of this study, combined with examining various factors that causes these profiles to deviate. This process began with the validation of porcine samples as a substitute of human samples through the identification of similar key indicators, characteristic to both tissues. Interestingly, different temperature ranges (pre- and post-ignition) and type of porcine tissues utilised were found to effect the type of key indicators detected; and as such, has convincingly resolved key indicators reported in previous research literature. In addition, key indicators of pure and blended textiles were also established and the effects of blended fibres towards the overall thermal properties of the textile, highlighted. Alterations to the key indicators of individual porcine and textile samples were examined, subjectively and objectively, when both samples were burnt together (combined samples). Subjective analysis involved the scrutiny of the chromatographic output, revealing the dominance of key indicators of porcine samples over textiles for majority of the combined samples. EIC and EIP proved to be a beneficial tool in extracting key indicators of porcine samples in the presence of contamination (textiles). At 70% presence, SOFM provided an objective and successful classification and discrimination of pyrolytic data according to the type of pyrolysis product detected across textiles, porcine bones and also in the combined textile-bone samples while underlining meaningful associations amongst similar groups. Overall, although this work suggests that pyrolytic data can be unpredictable, such as its dependence on various factors, with suitable analytical and statistical techniques, it has revealed pertinent information on the key indicators of porcine, human and textiles samples and the inter- and intra-molecular changes that occur to them during pyrolysis

Development and Assessment of a Decision Support Framework for Enhancing the Forensic Analysis and Interpretation of Fire Patterns

Fire investigators have historically relied upon fire damage as a means to conclude where a fire originated despite the lack of formal processes. The historical and current literature on the topic was evaluated with a specific emphasis toward the research conducted over the past eighty years related to fire patterns and their creation in the context of the fire environment. A seven step reasoning process for evaluating damage for determining the area of origin, along with a new definition for the term fire pattern, was developed. The aim was to develop and implement into practice a decision support framework that assists forensic fire investigators in assessing the efficacy of fire burn patterns as reliable indicators of the area of fire origin. This was facilitated by the development of a prototype method for determining the area of origin based on fire patterns analysis, named the Process for Origin Determination (POD). This dissertation describes the application of the POD with test subjects and presents an analysis of the outcomes showing its benefits. It has been shown through the use of reliability and validity tests that the POD assisted novices in more consistently and more accurately determining the area of origin over a variety of scenarios

A STUDY OF THE POTENTIAL EVIDENTIAL VALUE OF PERFUMES, ANTIPERSPIRANTS AND DEODORANTS IN FORENSIC SCIENCE

Perfumes and other fragranced products are abundant in our environment and are therefore likely to be abundant in a crime scene environment. They have properties which make them ideally suited to chemical detection and analysis but are currently underutilised as a potential source of evidence and intelligence. This work provides evidence supporting the hypothesis that such products have the potential to be forensically useful when analysed using modern analytical instrumentation. Gas Chromatography (GC), Fourier Transform Infrared Spectroscopy (FTIR) and High Performance Liquid Chromatography (HPLC) were each evaluated for their ability to distinguish between perfumes, deodorants and antiperspirants. GC analysis proved to be straightforward and provided sufficient detail to distinguish between products using visual pattern matching and statistical tools such as principal component analysis. FTIR was also able to discriminate between products with some success but it was felt that HPLC produced results with insufficient product detail to distinguish between perfumes. Using GC as the primary analytical technique, further experiments explored the most appropriate ways to store samples, recover liquid deposits from a crime scene and analyse a suspect or victim’s garments. It was also demonstrated that the change in composition of perfumes with evaporation follows a predictable pattern with forensically significant implications. This research has also established vital groundwork for future study into individual chemical profiles and lifestyle indicators

Chemometrics in forensic science: Approaches and applications

Forensic investigations are often reliant on physical evidence to reconstruct events surrounding a crime. However, there remains a need for more objective approaches to evidential interpretation, along with rigorously validated procedures for handling, storage and analysis. Chemometrics has been recognised as a powerful tool within forensic science for interpretation and optimisation of analytical procedures. However, careful consideration must be given to factors such as sampling, validation and underpinning study design. This tutorial review aims to provide an accessible overview of chemometric methods within the context of forensic science. The review begins with an overview of selected chemometric techniques, followed by a broad review of studies demonstrating the utility of chemometrics across various forensic disciplines. The tutorial review ends with the discussion of the challenges and emerging trends in this rapidly growing field