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Estimating the minimum PMI (mPMI) based on larval age involves identifying the species, reconstructing the thermal history at a crime scene, and modelling the rate of development. However, few studies take into consideration the mass-generated heat produced by larvae co-existing in an aggregation. These localized increases in temperature are often highlighted in the literature as having an influence on larval development, but there are ongoing difficulties with incorporating this concept into mPMI estimates. This is mostly due to a lack of research on the topic, particularly with controlled laboratory experiments or in natural conditions simulations. The aim of this research was to determine whether heat generation varied in different sized aggregations and, if so, did it influence larval development and behaviour. Various sized aggregations (50-2500 larvae) composed solely of Lucilia sericata (Meigen, 1826)(Diptera: Calliphoridae) larvae were reared in the laboratory at a constant ambient temperature of 22 °C (±1 °C). Data loggers and a thermal imaging camera were used to record mass temperatures throughout the feeding stage of development. Larvae were sampled from these different sized aggregations at set times and had their instar determined and/or their lengths and fresh weights recorded so that developmental rates could be monitored. To investigate the movement of larvae as they fed in an aggregation, individuals were tagged with a fluorescing elastomer. These larvae were easily distinguished from the rest of the cohort, which allowed their positions within the mass to be recorded at regular intervals. The results showed a strong positive relationship between mass size and the amount of heat generated by the aggregation (p<0.001), with temperatures rising as masses increased in size. A minimum mass size of 1200 larvae was required for the local temperature to increase significantly above ambient, with aggregations of 2500 larvae producing temperatures that exceeded ambient by up to 14 °C (± 1.2 °C). Larvae sampled from increasingly large masses showed an accelerated rate of development during the 2nd and 3rd instar. This coincided with when masses were at their warmest. These faster growth rates resulted in larger aggregations entering the post-feeding phase of development an average of 13 hours earlier than smaller, cooler masses. Physical measurements taken from larvae at 70 hours development demonstrated that individuals sampled from larger masses were significantly longer and heavier than those sampled from smaller aggregations (p<0.001). This provided further evidence of faster growth rates. However, when compared to solitary larvae, all mass-reared larvae, regardless of the size of the aggregation, appeared to benefit from a faster rate of development, reduced mortality and larger body sizes at dispersal. Larvae were observed to be in a constant state of motion and continually repositioned themselves within the mass, rotating between the periphery and the centre where they presumably fed. The thesis highlights the need to incorporate mass temperatures into forensic casework when using larval development to estimate the time of death. Larvae sampled from large masses, particularly during the 3rd instar, could appear older than they actually are due to the accelerated rates of development experienced under warmer conditions. If this isn’t taken into consideration then it could result in an overestimation of the mPMI. Future research should focus on identifying how other variables influence heat generation in masses, as well as finding ways to estimate the size of a mass, and hence its thermal history, at a crime scene.

Short tandem repeat typing is the primary method of DNA identification used in the field of forensic science. Over the past several years the need to improve on this method has moved to the forefront of research. Due to the increasing number of criminal cases and the substantial backlogs most laboratories are facing, it is vital to evaluate methods which can produce quality DNA profiles in a fast and reliable manner. Direct amplification, also referred to as direct PCR, is one alternative method that has been proposed to address this issue. Direct amplification allows for the generating of DNA profiles without using the DNA isolation process. While direct PCR would reduce processing time and resources, it is unknown if this technique would be able to generate a robust full or partial profile from samples which could be collected from scenes of crime. Often crime scene personnel must use visualization techniques, either in powder or chemical form, in order to see and collect biological evidence for submission to a crime laboratory. In order to evaluate if direct PCR is a feasible solution a comparative study between a direct PCR kit and standard DNA profiling practices was undertaken using mock crime scene type samples. Samples of this nature include surfaces which have been exposed to fingerprint powders and whole blood which has been chemically enhanced for visualization. PowerPlex® 18D, a direct amplification system, and PowerPlex® 16HS, an extraction-based method, were used to produce the profiles. An assessment of the kits aimed to critically evaluate and compare how the direct amplification kit performs on samples which have been exposed to powder and chemical processing for visual enhancement. This will be done by reviewing two types of samples; epithelial cells which have been exposed the fingerprint powders (black, magnetic and white) and whole blood which has been exposed to chemicals (luecocrystal violet, amido black and ninhydrin). Samples subjected to direct amplification using PowerPlex® 18D generated DNA profiles with greater peak heights when compared to the extraction- based method. The peak balances for heterozygous loci were also higher and more full profiles were generated with direct amplification than with the extraction method. The amount of DNA retrieved from each substrate also varied even though the same amounts of starting material were deposited, proving that the type of substrate can affect the retrieval of DNA. Epithelial cell samples were most successful when processed with white powder. Magnetic powder samples also yielded a positive result when using direct amplification which was not expected as in previous data magnetic powder samples have not been successful. Whole blood samples which were processed with amido black produced profiles with lower overall peak heights when compared to the two other chemical processes. This could be attributed to the rinse step which is required when working with amido black. Ninhydrin was the most successful of the chemicals in generating full, good quality profiles.

This PhD aimed to understand the constructs of aggression motivation and inhibition among prisoners. The research explored the role of developmental, affect, personality and socio-cognitive factors in aggression, investigating how these factors contributed to motives and inhibitors. This addressed several gaps in our knowledge and understanding of these factors among prisoners. In doing so, it contributed to the proposal of an empirically informed developmental model of aggression motivation and inhibition for prisoners, a model potentially capable of accounting for the theoretical and clinical limitations of existing explanatory models. Study one involved 206 adult men from a medium secure prison. This study specifically examined the role of aggression (using the Aggression Motivation Questionnaire, AMQ; Ireland, 2007) and offence motivation (with the Offence Motivation Questionnaire, OMQ; Gudjonsson & Sigurdsson, 2004) and affect (using the Multidimensional Anger Inventory, MAI; Sigel, 1989). Contrary to predictions, aggression motivation extended beyond the traditional reactive versus proactive distinction, with four core motivations identified. Further challenging the previous dichotomous distinction were findings that affect was related to all motivations and not just reactive aggression. The structure of offence motivation was consistent with previous research suggesting the validity of such motivation. Relationships found between individual offence and aggression motives supported longstanding notions in the human motivation and rationale choice literature that a limited number of motivations are capable of accounting for the diversity of human behaviour. Study one strengthens the argument to further examine and understand the factors contributing to such aggression motivations, such as cognition or developmental and life course experiences. Study two recruited 210 adult male prisoners to examine the developmental and socio-cognitive factors underpinning aggression motivations. Confirmation as to the structure of aggression motivation was also evaluated. It was predicted that differing developmental and socio-cognitive factors would relate to each motivation. Analysis supported this and thus further understanding was achieved as to the contribution of these factors. Reformulation of existing developmental models of aggression and the importance of social cognition for adult prisoners were consequently highlighted. However, attempts to confirm the four-factor solution for aggression motivation identified in Study 1 was not achieved. Exploratory factor analysis supported the extraction of a three-component solution from the AMQ, which was underpinned by ‘protection’, ‘pleasure’ and ‘positive outcomes’ motivations. This raised doubt as to the underlying structure of aggression motivation, which required further examination. Study three involved 234 prisoners from two separate prisons. All participants were adult men. This study facilitated the further exploration of maladaptive personality and affect regulation strategies in aggression motivation. Evaluation of the components of aggression inhibition was also undertaken. As expected, personality and affect regulation strategies were individually associated with aggression motives and inhibitors. This suggested that these factors had a unique contribution to aggression motivations and inhibitors. A four component structure for aggression inhibition was identified through exploratory factor analysis. The three factor structure for aggression motivation indicated by Study 2 was supported by confirmatory factor analysis. The findings gained from this study were combined with previous studies and influenced the development of the Applied Integrated Model of Aggression Motivation (AIM-AM). This new proposed integrated model of aggression is described in detail in the last Chapter of this thesis. The current research highlights the importance of considering aggression motivation and inhibition by demonstrating how valuable information to assist our understanding of aggression can be enhanced through their detailed examination. This research points towards a range of underlying factors which motivate and inhibit aggression in prisoners, including personality traits, developmental and life experiences, cognition and affect regulation. This was drawn together in the AIM-AM, which remains the first proposed aggression model developed specifically from the study of forensic populations. This applied theoretical model and underpinning research has a range of research and clinical implications for those working with prisoners, such as guiding the psychological assessment and risk evaluations of prisoners and focusing interventions to reduce their likelihood of aggression.

Research has suggested that primary psychopaths may be more instrumentally violent, and secondary psychopaths more reactively violent. The aim of the thesis was to conduct a systematic literature review identifying studies of importance within the area of psychopathy and violence. Results for this review concluded that there is a primary and secondary psychopathy distinction and that primary psychopathy is associated with instrumental violence and secondary psychopathy is closely linked to reactive violence. Therefore the research aims were to compare subtypes of psychopathy in terms of instrumental and reactive violence. The study subtyped pre-diagnosed psychopaths using a dimensional measure of personality, the Multidimensional Personality Questionnaire (MPQ-BF) (Patrick, Curtin & Tellegen, 2002). A total of 40 participants with a high psychopathy score and a history of violent offences were recruited. Results from the research were analysed using model based cluster analysis which replicated previous findings of two distinct psychopathy groups. Findings suggested the primary psychopath group (n = 12) had a trend towards instrumental violence, while secondary psychopath group (n = 28) were more evenly distributed amongst instrumental and reactive violence subtypes. This is broadly consistent with previous findings in terms of the characteristics of psychopathy subtypes and, to a lesser extent, their expected propensity for different types of violence. Finally, the MPQ-BF was analysed and critiqued to establish its validity and reliability within research. It was concluded that there was a need for the questionnaire to be normed on a number of varying populations to increase generalisability.

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