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Since its official introduction in England and Wales during 1985, the formal cautioning of adult offenders by police has grown to become a significant mechanism by which certain offenders are diverted from the criminal justice system. Currently some 30% of adult male offenders and 45% of adult female offenders arrested by the police are dealt with in this way. Cautioning is a procedural mechanism by which the police, contingent upon their adherence to the provisions of national guidelines, can elect to deal with certain criminal cases by means other than prosecution. Instead, they can choose to 'divert' the suspect from the court system by administering a formal caution; signed for by the suspect; often accompanied by verbal censure by a senior police officer; recordable on centralised police criminal indices; subject to the allocation of a CRO (criminal records office) number and citable in any subsequent court proceedings as a previous finding of guilt. The official rhetoric of cautioning espouses the virtues of benevolence through the provision of a second-chance for first time and petty offenders, allowing them to turn away from further offending, as well as efficiency through the speedy and timely management and disposal of cases not considered to be in the public interest to prosecute. But the burgeoning use of formal cautioning by the police has created problems of inconsistency, inequity and misapplication through repeat cautioning and its inappropriate use in cases of serious crime such as rape and murder. The fundamental principles of cautioning have also been criticised for eroding a suspect's due process rights such as the right to trial, the right to have prosecution evidence rigorously tested through an adversarial process that secures the right to legal counsel, a process that demands proof beyond reasonable doubt and which is subject to external review through an appeals process. These safeguards are almost completely absent with cautioning. Furthermore, the mechanisms by which police cautioning decisions are regulated have also been found wanting following research that suggests that the national guidelines are poorly defined, non-prioritised and provide for excessive latitude for police decision makers. This research project is an investigation into both the theory and practice of formal adult cautioning by the police. At its centre is a two-year covert participant observational study of the police work-world and of the ways in which cautioning, as intentional social action, draws meaning from and can be located within this occupational culture. Building upon a comprehensive review of available literature and consideration of the methodological and ethical issues created by the research, the thesis sets out to examine the true nature of the cautioning of adult offenders by the police in its natural setting - the custody office - and uses data drawn from officer and suspect interactions as the basis for a detailed analysis of how, why and by whom cautioning decisions actually come to be made. From this analysis conclusions have been drawn and recommendations made concerning how this disposal method might develop in the future and how existing problems might be overcome leading to a new, more consistent and equitable system of cautioning.

Fingermarks are believed to be unique to each individual and hence play a pivotal role as a form of evidence. However, despite significant ongoing research into fingermark recovery techniques, there are still many areas that need to be explored. Due to the immense potential of fingermarks as an effective method of identifications an attempt has been made in the present work to analyse one particular area that has been overlooked - the impact of wetting properties of different surfaces. The aim of the study is to investigate the physical and chemical changes in fingermark constituents deposited on polymer substrates of different water contact angles when recovered using the cyanoacrylate fuming technique with the use of camera and FTIR spectroscopy. The effect of aging and the environmental conditions on latent fingermarks was also studied. Meanwhile, visualisation of latent fingermark on metal substrates developed using the conventional technique (cyanoacrylate fuming and staining) was compared with the chemical images obtained from ToF-SIMS. Images from optical microscope showed the influence of substrate wetting properties in the distribution of both types of sweat material (sebaceous and eccrine) which in turn affected the cyanoacrylate polymerisation. On hydrophilic substrates, the fingermark was deposited as a continuous film that allowed higher cyanoacrylate polymerisation whereas on hydrophobic surfaces an irregularly shaped fingermark deposit led to lower amount of cyanoacrylate polymerisation. Aging of fingermarks was shown to be influenced by the underlying substrate wetting properties as fingermark constituents decreased more rapidly on hydrophobic surfaces. The eccrine fingermark aged significantly faster than sebaceous fingermark due to the more volatile nature of the fingermark constituents. Experimental evidence showed that both types of marks developed well by producing a clear fingermark pattern with cyanoacrylate fuming after aged for a week when the marks were not exposed to environmental conditions in comparison to the marks that were aged for the same period of time but exposed to airflow and light. The chemical images from ToF-SIMS demonstrated an exceptional quality of fingermarks (clear ridge definitions and sweat pore position) on the metal surfaces for periods of up to 26 days after deposition when the samples were stored at ambient conditions whereas conventional techniques showed little to no evidence of fingermarks being present on the metal surfaces after a few days.

Every year the police receive around a quarter of a million reports of missing people in England and Wales alone. Missing Incidents are not only traumatic and potentially dangerous for those involved, but are also likely to contribute to overall public spending; both with respect to the resources required for Missing Person searches, but also due to the increased likelihood of the breakdown of familial care following difficult to manage behaviours. Effective responses to these incidents are imperative, but there is little understanding of how missing person incidents unfold from the perspective of carers and parents. The thesis draws together several disparate research areas, alongside original research, which helps to elucidate how those responsible for a person with care and support needs search, navigate and make decisions under stress and lays a framework of understanding for future research. The work described in this thesis takes a three stage approach; description, prediction and intervention, in order to develop a systematic understanding of how missing incidents unfold, how decision-making within missing incidents can be predicated, and ultimately how technology could be used to address the problem. An initial interview study describes how missing incidents unfold and identifies the important decisions made by carers and search and rescue volunteers. Using this understanding, a vignette study was conducted which led to the development of a predictive model of behaviour during missing person search and the identification of factors which influence decision-making under these conditions. Effective communication is a crucial requirement for carers conducting Missing Person searches; both for material assistance and emotional support. Based on these findings, the final study of this thesis tested a novel prototype technology using an experimental design in a naturally occurring environment. Several evidence-based recommendations were produced as a result of this work which are intended to inform the design of new technologies for supporting missing person searches and may be of use to technology developers, policy-makers, care providers and other stakeholders.

This thesis introduces new perspective of addressing skull sex determination by investigating the possibility of using computer vision based solutions for sex determination from skull data, and developing new algorithms tailored for mitigating the underlying problems experienced in the conventional forensic sex determination methods. First, this thesis proposes the use of state-of-the-art 3D local shape descriptors to derive patch based representations from the skull. This is achieved by geometrically partitioning the skull into local regions, and aggregating the features from the regions into compact representation, which summarize the regional shape properties. Several rigorous experiments are conducted using this approach, and the results show that the proposed patch based representation is comparable to conventional forensic methods with a sex prediction rate of 86%. Traditional morphometric analysis on the same dataset produced prediction rate of 86.4%, while PCA/LDA based method produced prediction rate of 75% which indicates that the proposed patch based representation is competitive and an effective method of sex determination. Second, this thesis proposes a new approach of partitioning the skull into pseudo-anatomical regions, which is reminiscent of the anatomical regions commonly examined in forensic morphological assessment. In order to achieve this, the skull samples are registered to establish correspondence across the dataset using an improved version of coherent point drift (CPD) algorithm named Ensemble CPD. The correspondence established is exploited to partition the skulls using Fuzzy cmean (FCM) into regions which share visual resemblance with the anatomical regions in forensic morphological assessment. Further, 3D local shape descriptors are computed from each region, aggregated into compact representation, and eventually used for sex determination. The best result in this experimental evaluation is 86.5% which is also comparable to conventional forensic methods. Finally, this thesis proposes two group variable selection algorithms which are (1) novel group regression model for manifold data and (2) novel group regression model for manifold data with split augmented lagrangian algorithm, for automatically discovering discriminant (important) skull regions. The main objective of these methods is to prune out the salient regions of the skull that contribute positively to sex prediction performance. Forensic methods have demonstrated that some anatomical parts are more sexually dimorphic than others, however such analysis is performed using stepwise variable selection. Thus, this thesis introduces new techniques for automatically learning such information directly from the data. The best result in this experiment is 84.5% which is comparable to conventional forensic methods.

This research seeks to characterise the GC amenable lipid component of soils as a means of discriminating between them based on subtle differences in the determined whole distributions. Furthermore, the use of models based on the results obtained, was explored as a means of potentially identifying soils of unknown origin, i.e. those that may constitute forensic evidence obtained as part of a criminal investigation. The work establishes a lipidomic workflow for characterising soils, three scenarios are considered: (1) soils from different geographical locations, (2) soils from the same location but under different land-use, and (3) peat samples dominated by two species of vegetation. The effect of seasonal change was also investigated. An analytical workflow was developed and comprised ultrasonic extraction and saponification yielding a total lipid extract. Accurate mass GC-MS was used to analyse extracts and the acquired data processed using Mass Hunter Profinder B.08 and Mass Profiler Professional. The results were assessed using principal component analysis (PCA) and hierarchical clustering analysis. An un-paired t-test and Kruskal-Wallis test were performed on each data set to select discriminant entities responsible for the observed clustering. Partial least square discriminant (PLSD) models were built to classify unknown samples. For (1) results revealed a distinct separation, based on land-use and vegetation, for the eight sites studied. Established biomarkers, e,g, dehydroabietic acid (DHAA) for pine (highest levels at the coniferous sites), were among the discriminant entities selected. For (2) this approach separated four close-proximity plots from Broadbalk long-term experiment based on the overlying vegetation arising from differing land-use (wooded, grazed, stubbed and winter wheat). Another long-term experiment, Park Grass, showed separation based on soil pH and species diversity where four clusters were observed from an extremely acidic plot (3.7), to a slightly acidic plot (5.7), control plots (5.9 and 6.9) and higher pH plots (6.5 to 6.9). Finally, (3) enabled discrimination between two peats dominated by sedge and Sphagnum. Artificial peat mixtures of sedge and Sphagnum were separated in accordance with origin along PC1 in the PCA. PLSD models gave 100 % correct prediction for both Broadbalk and peat samples showing the potential of this method for characterising soils of unknown provenance. Overall, this work demonstrates that lipidomics offers a rapid, means for profiling soils applicable to a diverse range of forensic (and wider) contexts.