The current methods for identifying ignitable liquid residues in fire debris are heavily based on the holistic, qualitative interpretation of chromatographic patterns with the mass spectral identification of selected peaks. The identification of neat, unweathered ignitable liquids according to ASTM 1618 using these methods is relatively straightforward for the trained analyst. The challenges in fire debris analysis arise with phenomena such as evaporation, substrate interference, and biodegradation. These phenomena result in alterations of chromatographic patterns which can lead to misclassifications or false negatives. The biodegradation of ignitable liquids is generally known to be more complex than evaporation [20], and proceeds in a manner that is dependent on numerous factors such as: composition of the petroleum product/ignitable liquid, structure of the hydrocarbon compound, soil type, bacterial community, the type of microbial metabolism that is occurring, and the environmental conditions surrounding in the sample. While nothing can be done to prevent the biodegradation, continued research on biodegraded ignitable liquids and the characterization of the trends observed may be able to provide insight into how an analyst can identify a biodegraded ignitable liquid residue. This research utilized normalized abundance values of select ions from pre-existing gas chromatography-mass spectrometry (GC-MS) data on samples from three different gasoline and diesel biodegradation studies. A total of 18 ions were selected to indicate the presence of six hydrocarbon classes (three each for alkanes, aromatics, cycloalkanes, naphthalenes, indanes, and adamantanes) based on them being either base peaks or high abundance peaks within the electron impact mass spectra of compounds within that hydrocarbon class. The loss of ion abundance over the degradation periods was assessed by creating scatter plots and performing simple linear regression analyses. Coefficient of determination values, the standard error of the estimate, the slope, and the slope error of the best fit line were assessed to draw conclusions regarding which classes exhibited desirable characteristics, relative to the other classes, such as a linear degradation, low variation in abundance within the sampling days, and a slow rate of abundance loss over the degradation period. Additional analyses included two-way analysis of the variance (ANOVA), to assess the effects of time as well as different soil type on the degradation of the hydrocarbons, stepwise multinomial logistic regressions to identify which classes were the best predictors of the type of ignitable liquid, and one-way ANOVAs to determine where the differences in the ratios of hydrocarbon classes existed within each of the ignitable liquids, as well as between the two liquids. Hydrocarbon classes identified as exhibiting characteristics such as slow and/or reliable rates of abundance loss during biodegradation are thought of as desirable for future validation studies, where specific ranges of hydrocarbon class abundance(s) may be used to identify the presence of a biodegraded ignitable liquid. Classes of hydrocarbons that have experienced biodegradation that maintain an abundance close to that of a neat, non degraded counterpart, or that reliably degrade and have predictable abundance levels given a particular period of degradation, would be instrumental in determining whether or not an unknown sample contains an ignitable liquid residue. It is the hope that these assessments will not only provide helpful information to future researchers in the field of fire debris analysis, but that they will create interest in the quantitative, statistical assessment of ignitable liquid data for detection and identification purposes.

Gasoline is a substance commonly encountered in forensic settings. Unfortunately, gasoline is an easily obtainable ignitable liquid that arsonists commonly use to initiate or expedite the spread of an intentionally set fire. Fires claim the lives of many people each year in addition to causing widespread property damage. Many fire scene investigations result in charges of arson, which has the legal connotation of a committed crime. For this reason, extensive analysis and investigation must be undertaken before any suspected arson scene is deemed an actual case of arson. Although ignitable liquids, including gasoline, may be present at the scene of a fire, it does not necessarily mean they were intentionally used as accelerants. An accelerant is a fuel used to initiate a fire. These realities, in addition to several other factors, demonstrate why a rapid, reliable, gasoline analysis method is crucial to forensic applications. In this thesis, direct analysis in real time – mass spectrometry (DART-MS) is evaluated as a potential method that could better identify, distinguish and classify gasoline brands from one another. Techniques such as DART-MS could enable forensic laboratories to better identify questioned gasoline samples. Many ignitable liquids share similar chemical properties, and forensically relevant evidence is often obtained from a crime scene in less than favorable conditions. Fire debris can encompass various materials, including burnt carpet, flooring, items of furniture and clothing, among others. If gasoline was used as an accelerant, it may be present in trace amounts after the termination of the fire. Materials submitted for laboratory analysis may be substrates with compositions that have components similar to those found in some ignitable liquids. These are just a few of the potential obstacles that could be encountered with analyzing fire debris in a forensic setting. Traditionally, gas chromatography – mass spectrometry (GC-MS) methods are utilized for gasoline analysis in the criminal laboratory setting. While traditional GC-MS methods are sensitive and able to classify samples as gasoline, they are time consuming in terms of both sample preparation and analysis. Additionally, they do not generate differential mass spectral data based on the brand of gasoline. Conversely, gasoline analysis in this research, utilizing the DART-MS method, demonstrated that five different brands of gasoline could be distinguished from one another both by visual examination of mass spectra and with methods of chemometric analysis. Advantageously, the DART-MS method, an ambient ionization technique, requires little sample preparation and a rapid sample analysis time, which could drastically increase the throughput of standard sample analysis with further method development. The goals and objectives of this research were to optimize the DART-MS parameters for gasoline analysis, determine if DART-MS analysis could distinguish gasoline by brand, develop chemometric models to appropriately classify gasoline samples, and finally lay groundwork for future studies that could further develop a more efficient and discriminating DART-MS gasoline analysis method for forensic casework. Each brand of gasoline was observed to have a chemical attribute signature (CAS) consisting of not only low-mass ions, but also a variety of high-mass ions not usually observed with gasoline samples analyzed by GC-MS. Although variables including season, storage time, dilution and age of the gasoline were observed to contribute to the resulting mass spectral data, once the mass spectra are better understood, they could offer even more discriminating power between samples than simple analysis of the gasoline brand. In this research, DART-MS parameters were first optimized for gasoline analysis. Subsequently, the five acquired brands of gasoline: Shell, Sunoco, Irving, Cumberland Farms and Gulf, were analyzed both undiluted (or neat) and diluted utilizing the DART-MS analysis method. GC-MS data was generated and analyzed to show comparisons. After analyzing the data generated by both approaches, it was apparent that the DART-MS method could generate CASs based on the gasoline brand and offer a degree of differentiation that traditional GC-MS does not. Additional chemometric analyses utilizing principle component analysis (PCA) and the construction of models with Analyze IQ Lab software verified that the gasoline brands were distinguishable when samples were analyzed with this ambient ionization method. PCA plots of the neat gasoline demonstrated clustering based on brand. Additionally, models constructed from training samples generated from DART-MS analysis of the various brands were able to accurately classify gasoline samples as "yes" or "no" when a test set of gasoline was compared to all five brands. The lowest associated testing error rate for some of these models was 0%. However, additional analysis with greater sample sizes needs to be further carried out to more accurately evaluate this method of gasoline analysis and classification.

In Ontario, fire investigators from the Office of the Fire Marshal (OFM) are responsible for determining the origin and cause of suspicious fires. As part of the investigation, fire debris samples are collected from the scene and analyzed by the Centre of Forensic Sciences. The standard practice is to collect items that are porous, highly absorbent or adsorbent with high surface areas as they allow for better retention of the ignitable liquids. The evidence typically collected includes carpets, cardboards, soils, cloths and other items that have not been impinged by flame such as beneath baseboards. These samples are analyzed for the presence of ignitable liquid residues which may be evidence that an accelerant was used at the fire. When a body is recovered from a fire it can provide another source from which to collect samples for analysis. These samples can be especially helpful in instances where the fire generated an intense heat which may cause a loss of ignitable liquid residues from the fire debris. The tissue samples have a greater likelihood of still containing residues as the organs and body fluids can act as a shield protecting the residues from volatilization. The purpose of this study is to validate whether a victim was alive or deceased at the time a fire was intentionally set by detecting presence or absence of gasoline residues within their lungs and heart blood post fire. It was hypothesized that only when a victim was alive and performing respiration would sufficient gasoline vapours enter the airways and bloodstream for detection postmortem. Contamination becomes a significant issue when these samples are collected at autopsy and this study aimed to determine the accuracy with which a gasoline signature can be interpreted following the collection and analysis of lung tissue and heart blood. Pig (Sus domesticus) carcasses were chosen as acceptable analogues for humans in this study. The experiments involved anaesthetizing a pig (with Animal Ethics Approval), exposing the pig to gasoline vapours for 10 minutes, and then euthanizing it. The carcass was clothed with a cotton t-shirt and placed in a house where additional gasoline was poured onto it. The house also contained two additional clothed pig carcasses which did not inhale gasoline vapours; one with gasoline poured directly onto it and the other with no gasoline exposure (negative control). Thermocouples were placed under each carcass and in the centre of each room at ceiling and floor level to record the temperature. The house was set ablaze and monitored by a volunteer fire service. After the fire had reached V flashover and was suppressed, the carcasses were collected and their lungs and heart blood excised at a necropsy. The lungs and heart blood were then placed into glass mason jars following the OFM protocol. The headspace from each sample was analyzed by thermal desorption-gas chromatography-mass spectroscopy to determine the presence or absence of a gasoline signature. Two full scale house fires were conducted in order to obtain three replicates. The results showed that only the lungs and heart blood from the pig that inhaled gasoline contained gasoline residues. This indicates that it is possible to determine a victim’s status at the time of the fire based on the detection of gasoline in the lungs and/or heart blood. It was also concluded that contamination of samples during an autopsy can be minimized by changing gloves before handling the internal tissues. The thermal data showed that the bodies act as an insulator and protects the underside as the temperatures under the carcasses did not exceed 30⁰C while the room reached over 900⁰C at the first full scale house fire. These results will impact the forensic community by demonstrating the importance of analyzing a deceased victim’s internal tissues for ignitable liquid residues post fire as they may provide evidence of an intentionally set fire as well as providing information about the victim’s status when a fire was started. These findings will have a direct impact to the OFM as additional evidence can be obtained by completing internal tissue analysis. This will intern impact the Centre of Forensic Science (CFS) as it confirms the importance of analyzing internal tissues in order to provide results to fire investigators. Finally these findings should be used to implement new protocols at the Coroner’s Office so contamination can be minimized during fire autopsies and accurate samples are collected and sent to the CFS for analysis. / UOIT

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