Exploring and understanding the practice of accurately assessing offenders is an important area of research for forensic practice and the risk management of offenders. This thesis aims to explore different approaches to offender assessment, specifically their clinical utility in forensic mental health settings. The first chapter, provides an introduction to the importance of accurate offender assessment, and presents current models proposed within the literature. The second chapter, provides a systematic review of historically used approaches in the assessment of risk, and compares their predictive accuracy and clinical utility in relation to a mentally disordered offending population. The third chapter, critically appraises a widely used assessment tool to assess risk within forensic mental health settings, the HCR-20 (Version 3.0; Douglas, Hart, Webster & Belfrage, 2013). The fourth chapter, moves way from specific tools used in current practice and instead explores clinicians current understanding and use of newer concepts in offender assessment (IOW/IOA), through a qualitative research study. Finally, the fifth chapter presents a thorough discussion of the overall content, findings and conclusions of this thesis. Findings have important implications for the practice of assessing and managing offenders effectively.

A systematic literature review summarizes what is known about the relationships between attachment, relational security and therapeutic relationships. A paucity of research with forensic populations is noted. Consequently the empirical research paper explores more systematically the relationships between these variables on forensic psychiatric wards. Suggestions for staff and service development are presented. No relationships were found between relational security and service users’ attachment to the service and between relational security and risk events and treatment outcomes. Additional analyses revealed that relational security and ward atmosphere were moderately correlated. A large positive correlation was found between patients’ attachment to the service and ward atmosphere, and a moderate, negative, relationship was found between patients’ attachment to the service and risk incidents Multiple regression revealed that relational security and ward atmosphere significantly predicted patients’ attachment to the service. More robust research is needed to investigate the relationships between attachment, relational security, risk incidents and treatment outcomes on forensic psychiatric wards. An argument is made for promoting stronger therapeutic relationships between staff and service users so that forensic wards can become closer to secure bases which might help clients to overcome past interpersonal traumas and develop safer ways to relate interpersonally.

In forensic investigations involving severely burned human remains, dental analysis stands alone as other means of identification are often destroyed. Therefore, the aim of the present work was to investigate the influence of duration of heat exposure and heating regimes regarding the macroscopic, compositional, structural and crystalline alterations of dental tissues. Experiments were carried out using 215 freshly extracted human teeth, exposed to temperatures of 400 to 1000°C. Shrinkage and shape preservation was analysed using micro-CT, whilst crystalline alterations were evaluated with synchrotron-based SAXS/WAXS experiments. The alterations of organic constituents were assessed using TGA and FTIR. Moreover, calibrated digital photographs were used to document and analyse colour alterations. Although dentinal shrinkage was found at 400°C, tooth morphology was well preserved even at 1000°C. Surface colour alterations were linked to the degradation of organic components, and were highly dependent upon the duration of heat exposure and the heating regime, whilst crystalline alterations were less influenced by these factors. The combination of novel analytical approaches enabled the documentation and quantification of heat-induced alterations of dental tissues, providing results that can be used in the forensic identification process and allow an improved estimation of the cremation temperature range based on human dental remains.

A língua humana foi primeiramente descrita por Andreas Vesalius, o “Pai da Anatomia Moderna”, no livro De humani corporis Fabrica em 1543. Contudo, as papilas do dorso da língua eram desconhecidas até então. Estas foram descritas e classificadas nos seus três tipos básicos de acordo com o tamanho em papilas de 1ª, 2ª e 3ª ordens somente após o advento do microscópio, por Marcello Malpighi em 1665. A partir daí, os padrões morfológicos das papilas variaram de acordo com a descrição de diferentes autores até alcançar os quatro tipos conhecidos até os dias de hoje, sendo elas: fungiformes, filiformes, folhadas e circunvaladas, sendo estas últimas o objeto de estudo do presente trabalho. Sugeridas primeiramente como tema de investigação para Alfonso Bovero (1871- 1937) fundador da Escola Anatômica de São Paulo pelo seu mentor Carlo Giacomini (1840-1898), Bovero criou um acervo na Faculdade de Medicina da Universidade de São Paulo (FM-USP) com mais de 800 línguas humanas obtidas de indivíduos masculinos e femininos, de diferentes idades e etnias. Em seu trabalho preliminar sobre o tema, publicado em 1936, ele descreveu o elevado grau de polimorfismo das papilas, agrupando-as a outros “instrumentos de função” como o encéfalo e as mãos humanas que, como órgãos da vida de relação, se caracterizam pela extrema complexidade morfológica. Com a sua morte em 1937, a pesquisa foi interrompida e do acervo inicial restaram 327 espécimes. O presente trabalho resgatou esse material a fim de avaliar com metodologias atuais a morfologia das papilas, levando em consideração a hipótese de individualidade lingual postulada inicialmente por Bovero, de que não existem duas línguas idênticas, nem mesmo nos antímeros de uma mesma língua. Para identificar os padrões estruturais e de possível singularidade das papilas disposição, número, área papilar, presença ou ausência de orla e formas tanto da própria papila quanto da sua orla foram utilizadas as técnicas de Morfometria, Mesoscopia, e Microscopias de Luz e Eletrônica de Varredura. Os resultados demonstram que no geral as línguas estão sobre 4 formas (circuliformes, trianguliformes, fusiformes e retanguliformes), as PCVs estão dispostas principalmente em forma de ”V” e “Y” linguais; elas podem ser verdadeiras ou falsas; algumas papilas apresentaram a mesma área, porém com morfologia diferente. Além disso, houve variação na textura dos componentes das PCVs. A combinação das variáveis estudadas (papilas, orlas, valo, poros gustatórios e histologia) confirmam a hipótese de unicidade glótica. Dessa forma, os remanescentes do acervo com um século de existência foram aproveitados, demonstrando viabilidade para o estudo anatômico e valorizando os experimentos iniciais do fundador da Escola Boveriana de Anatomia / The human tongue was first described by Andreas Vesalius, known as “the father of modern anatomy”, in the book De humani corporis Fabrica, published in 1543. However, at that time, the dorsal lingual papillae were still unknown. They were described and classified according to size in three basic types: 1st, 2nd and 3rd order papillae, only after the advent of the microscope, by Marcello Malpighi in 1665. Thereafter, the morphological patterns of papillae varied according to different authors' descriptions until reaching the four currently known types: fungiform, filiform, foliate and circunvallate. The later is the aim of this work. Influenced by his mentor, Carlo Giacomini (1840-1898), Alfonso Bovero (1871- 1937) founder of the School of Anatomy of São Paulo created an archive of over 800 human tongues, from male and female individuals, at different ages and different ethnicities at the School of Medicine of the University of São Paulo. In his early work on this subject, published in 1936, he described the high degree of polymorphism found among the papillae, classifying them as other "function instruments", such as the encephalon and the human hands, which, as organs of relation, are characterized by their high morphological complexity. With his death in 1937, this study was interrupted and currently only 327 specimens are left from the original archive. This work analyzed this material regarding papillae morphology with currently available technologies, considering the lingual individuality hypothesis initially proposed by Bovero, which states that there are no two identical tongues or antimers on a given tongue. To identify the papillae's structural and possible singularity patterns distribution, number, papillary area, presence or absence of rims, and shape of both the papillae and their rims we used morphometry, mesoscopy, and light and scanning electronic microscopy. Results show that, in general, tongues are presented in one of four shapes (circle, triangle, rectangles, and fusiforms); vallate papillae (PCVs) are distributed on the tongue mainly as V- or Y-shaped regions; they can be true or false; some papillae have the same area, but different morphologies. In addition to that, we found variation on the texture of PCVs components. In combination, the studied variables (papillae, rims, pits, taste pores, and hystology) corroborate the hypothesis of uniqueness of the tongue. Thus, the remaining of this one-century-old archive were used, viability for the anatomical study was showed, and the initial experiments of the Boverian School of Anatomy founder were praised

Loss of analyte from biological samples during the post-mortem interval or during storage has potentially serious implications in forensic toxicology and represents a challenge for the forensic toxicologist, especially in the interpretation of case results. The initial aim of the studies in this thesis was to evaluate the stability of some important drugs and compounds in blood under different storage conditions in order to optimize the preservation of these compounds. A second aim was to evaluate a new method of stabilizing these compounds in blood by storing them as dried blood spots on filter paper. The third aim was to investigate methods by which corrections could be made for analyte losses based on quantification of their degradation products, which would serve as markers of the former presence of the compounds even if they were no longer detectable. The background to toxicology and its classification systems is reviewed along with the most common areas of application, including forensic toxicology. Details are given of the most commonly-used matrices and of current problems facing forensic toxicologists, particularly the problem of analyte instability. The literature concerning stability of drugs and pesticides in biological samples are reviewed and discussed as well as methods applied to enhance and stabilize analytes for long storage periods. Background is provided on methodologies used in the work reported in this thesis, including extraction techniques and instrumental analysis by LC-MS/MS and GC/MS. Also, because of its importance in forensic toxicology at present validation procedures and requirements are also discussed. An initial study was made of drug stability during storage in blood samples for 1 year under conventional laboratory conditions using selected drugs from the benzodiazepine group, alprazolam, lorazepam, oxazepam and estazolam. Blank blood containing these drugs at low and high concentrations was stored in tubes at -20° C, 4°C and room temperature. Half of the tubes contained fluoride-oxalate preservative. Blood samples were analysed on the first (day zero), second and fourth days, and after one week, two weeks, one month, two months, three months, six months and one year using a method which was developed and validated for this study based on solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Alprazolam and estazolam were stable at -20° C and 4° C, but decreased by almost 10% at room temperature (RT) at both concentrations. Lorazepam and oxazepam were stable at 20°C but were poorly stable at 4° C and decreased by 100% at RT by the end of the 1 year period. Sodium fluoride stabilised the drugs by approximately 13% compared to unpreserved samples. The long-term stability of alprazolam and estazolam is attributed to the presence of the trizolo ring in their structures which makes the compounds more resistant to hydrolysis, the most prominent degradation reaction affecting benzodiazepines. A similar study was performed on the stability of morphine-3- and 6-glucuronide and codeine-6-glucuronide in blood and urine under the same storage conditions. These compounds were stable at -20° C, losing less than 7% but losses were higher at 4° C, up to 18% in blood and 28% in urine, and at room temperature up to 54% in blood and 78% in urine after 1 year. Sodium fluoride did not have a significant effect (<10% increase in stability). An investigation was carried out on stabilisation of hydrolytically-labile benzodiazepines and cocaine in blood during storage as dried blood spots (DBS) on filter paper. An analytical method was developed and validated for this study based on SPE and LC-MS/MS analysis. The drugs selected were flunitrazepam, temazepam, oxazepam, lorazepam, nitrazepam, diazepam and cocaine. Blood spots (100 µl blood) on Guthrie card 903 containing the drugs at 1000ng/ml were dried overnight at RT. Spots were cut out and extracted with buffer (pH 6), which was analysed with the validated method. DBS were stored in duplicate at RT, 4°C and -20°C for up to one year. Degradation of the drugs in DBS in all storage conditions was less than for the corresponding liquid blood samples stored under similar conditions. More than 80% of each analyte could be recovered from DBS after one month while 15 % cocaine and 74 % of the benzodiazepines were recovered after 1 year under all conditions. The degradation of diazepam, temazepam, chlorodiazepoxide and oxazepam by hydrolysis was studied over a 1 month period under conditions designed to accelerate the reaction (80 °C, pH 2 and 12) and the hydrolysis products 2-methylamino 5-chlorobenzophenone (MACB) and 2-amino 5-chlorobenzophenone (ACB) were analysed by a method based on SPE and LC-MS/MS which was developed and validated for this study. MACB and ACB in whole blood and urine were evaluated as indicators of the original drug concentrations. Blank blood and urine containing these compounds at 1000 ng/ml stored at high temperature (80°C) and under acidic (pH 2) and basic (pH 12) conditions at room temperature for one month. The samples were analyzed in duplicate at days 1, 2, 4, 7, 14 and 30. MACB and ACB were the main hydrolysis products and their concentrations increased as degradation of the drugs proceeded. They could be detected when the starting materials had completely disappeared. However, MACB and ACB were found to be further degraded under some of the conditions used and a further study was made of the conversion of MACB to ACB. It was concluded that the drugs studied were more sensitive to alkaline pH than to acidic pH or high temperature and that MACB and ACB can be used to confirm the original presence of these drugs in samples, especially when they have decomposed due to poor or prolonged storage conditions. A final study was made of organophosphates (OPs) and their dialkylphosphate (DAP) hydrolysis products. A new method was developed and validated for analysis of OPs and DAPs in blood samples based on SPE and GCMS after derivatization with N-tert-butyldimethylsilyl-N-methyltrifluroacetamide. The influence of sodium fluoride preservative and storage as DBS on filter paper on the stability of OPs in blood was assessed over a 3 day period at RT. With preservative, DAPs concentrations increased as degradation of the OPs proceeded and they could be detected when the parent compounds had completely disappeared. OPs in DBS showed good stability in comparison to liquid blood samples containing NAF and the parent compounds were detected at the end of the observation period. It was concluded that careful attention should be given to the storage of samples to avoid loss of analyte and erroneous interpretation of results. DBS could be an effective and inexpensive way of increasing analyte retention but routine use of preservatives without evaluation of their effects is discouraged, as these may accelerate loss of analyte.

Background: The Mental Health (Care and Treatment) (Scotland) Act 2003 reduced the role of the nearest relative, identified by a hierarchy of relationships, who previously could admit and discharge a patient as well as receive information about their care. This role is now reduced to one of receiving basic information only and the hierarchy for identification has been modernised. Service users may now nominate a named person with similar rights to service users to help protect their interests. This person cannot admit or discharge but is entitled to information and consultation about their care. If a patient has not appointed a named person, then the primary carer is appointed by default and, if there is no primary carer, the nearest relative assumes the position. Aims: To explore service users’, carers’ and professionals’ perceptions and experience of the named person provisions. Method: Twenty service users, ten carers, seven MHOs and nine professionals with influence on government policy were interviewed about their experiences. Interviews were carried out face-to-face (service users and some carers) and by telephone (carers, MHOs and policy influencers). The resulting transcripts were analysed using thematic analysis. Findings: The majority of all interviewees welcomed the introduction of the named person provisions because of the increased choice it gave service users. Service users often did not wish to nominate their nearest relative, many choosing to nominate a friend. Important factors in making a nomination were that the nominee knew the service user’s wishes and could be trusted to carry them out. Some service users chose not to nominate relatives to spare them responsibility. However, the provisions were not without their problems; uptake was perceived to be low and there were particular problems in relation to the level of understanding of the implications of a nomination by service users and of the lack of accessible information and support to increase this understanding. The imbalance of power in relationships between service users, carers and professionals was thought to impact on the autonomous choices of service users and carers. Further problems were identified with named persons appointed by default in relation to service user choice and confidentiality. Conclusion and recommendations: Although the choice is welcome to some service users, there appears to be a lack of full understanding of the role, and continued awareness-raising is required with service users, carers and professionals which should further be supported by accessible information for both service users and carers. There is currently a lack of support for carers in particular and it is recommended that this be addressed using carers’ services. It seems that many named persons are being appointed by default (itself an anomaly in Scots law) which threatens human rights, because of the lack of choice of the service user about who is involved in their care and their inability to prevent the sharing of confidential information with the default named person. The current lack of a right of service users to reject having a named person at all restricts choice and autonomy, and may further place unwanted responsibilities on carers and relatives which are difficult to remove. To ensure that service users’ rights are fully protected, the named person should become an optional nominated position and the default mechanisms removed.

In Part I, the most useful methods for the estimation of the time of death are reviewed, with special emphasis being placed on the post-mortem rate of cooling because this method is commonly used for estimating the interval after death. Theories and models of the post-mortem loss of heat from the human body are summarised and discussed. The Microwave Thermography System, a new device which is applied to this field for the first time, is described and its mode of operation is discussed. Using this device, it is possible to measure temperatures of internal organs of the body by placing the sensory elements on the skin. The reliability of the system and factors affecting the accuracy of temperature measurements made with the device are assessed and discussed. Results of a study of the cooling rate of 117 fatalities are given. All cases were studied under controlled conditions and two groups were collected in which the bodies were monitored either naked or covered with blankets. In each case, the environmental temperature as well as the temperatures at three body sites were continuously monitored over a period beginning shortly after death and ending up to 60 hours post-mortem or more. Rectal and environmental temperatures were measured with thermocouples while the temperature of the brain and liver were measured using microwave probes, therefore by non-invasive and ethically acceptable methods. The data were recorded on tape following Analogue to Digital (AD) conversion using a BBC Microcomputer. These data were processed and temperatures at the moment of death for the three body sites were estimated by extrapolation backwards. Processed data were transferred to a mainframe computer where sophisticated curve-fitting procedures were performed. These indicated that the cooling curves were adequately represented by three-term exponential equations containing six empirically derived parameters. Statistical analysis of the parameters yielded average formulae and the use of these formulae to improve the ease and accuracy of the estimation of the time of death is discussed. Lastly, suggestions for future work are given. In Part II, biochemical methods of estimating the time of death are reviewed and limitations of their use are duscussed. Steroids were selected as potential indicators of the post-morem interval by virtue of their metabolism and degradation after death. Aspects of steroid biochemistry are summarised. Various methods of steroid analysis were assessed using radioassays and thin layer chromatography. Three reversed phase chromatography systems were evaluated for separation and recovery of steroids extracted from blood, tissues and faeces. The use of different numbers of Sep-Pak C18 cartridges for the purification of steroid extracts was examined and steroid recoveries were measured and compared. The results indicated that recoveries were best when 4-6 cartridges were used. Rapid and slow procedures of enzymatic hydrolysis and acidic solvolysis of steroid conjugates were compared. A new and relatively rapid method for analysis of steroid profiles in biological samples was developed. Assessment of this method showed that steroid recoveries were improved compared to existing methods. A pilot study of the post-mortem changes in the steroid profiles of blood, tissues and faeces was carried out using the rat as a suitable and convenient animal model. Liver and adrenal tissues, faeces and blood samples collected from 30 rats either at the moment of death or 24 hours after death were analysed and their steroids were studied qualitatively and quantitatively using selctive ion monitoring GC-MS techniques. Thus chromatographic peaks were identified by comparison of their retention times and mass spectrometric characteristics with those of standards and quantitative analysis was performed. The occurrence of significant steroid changes was difficult to ascertain but some changes in the steroid profiles of the biological samples were shown to have occurred. Lastly, the practicability of this method for the estimation of time of death is discussed.

This thesis examines the use of nail as an alternative biological specimen in forensic toxicology. Nail is a difficult analytical matrix from which to extract drugs because of its tough physical composition, based on keratin. The initial part of the project investigated the use of a cryogenic grinding method for fingernail clippings. Grinding at liquid nitrogen temperatures was found to be an effective procedure and the conditions were optimised to a two or three cycle programme of freezing and grinding. Small particle sizes were obtained of approximate size 1µm. It was established that drugs could be extracted directly from nail powder with a range of solvents without the need for alkaline hydrolysis. Methanol was found to be the most effective extraction solvent, which also gave the lowest number of co-extracted interfering compounds. This procedure was subsequently used with nail samples from different types of forensic cases, including cannabis, heroin and steroid abusers. Cryogenic grinding of nail was evaluated as an extraction method for cannabinoids in nail clippings from chronic cannabis smokers. This method was also compared to the alkaline hydrolysis method. Fingernail clippings were collected with prior informed consent from volunteers attending the Edinburgh Drug Addiction Study (EDAS) clinic. The collected nail clippings were decontaminated and divided into two groups: the first group was extracted with methanol after pulverisation in a liquid nitrogen cryogenic mill; the second was extracted with ethyl acetate after hydrolysis in sodium hydroxide. In both groups deuterated cannabinoids were used as internal standards. Both sets of extracts were derivatised with BSTFA before being analysed by gas chromatography – mass spectrometry (GC-MS). Cannabidiol, ?9-tetrahydrocannabinol and 11-hydroxy-?9-tetrahydrocannibinol were quantified in both sets of extracts. 11-nor-?9 –tetrahydrocannabinol-9-carboxylic acid was only identified and quantified in the extracts resulting from the cryogenic grinding method. Cannabinoid concentrations were very low, in the range 0-4 ng/mg. These results strongly support the use of nail as a biological specimen for the detection and quantification of past exposure to cannabis, and secondly, they indicate that grinding with a cryogenic mill is a useful procedure, which yields simultaneous results for the primary psychoactive cannabinoid and its metabolites. Cryogenic grinding was then evaluated for the extraction of opioids in nail in comparison with the conventional alkaline hydrolysis method. Finger and toe nails were collected from donors with informed consent.

The aim of this study was to investigate new methods of analysis which might be applied to forensic toxicology problems including those resulting from pesticides, particularly the quaternary ammonium herbicide group, and from drugs, particularly the benzodiazepine group. In the first part of this study, an efficient method for the determination of quaternary ammonium (QA) compounds (pesticides and drugs) in human whole blood was developed. The second part of this study concerned the development of a novel sorbents for solid phase extraction using molecularly imprinted polymers (MIPs). The approach adopted was initially to synthesise a known MIP using diazepam as template then to prepare novel MIPs using other benzodiazepines and analogues of QA compounds as templates. In the first of these stages, an anti-diazepam MIP was synthesized using methacrylate acid (MAA) as the monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-liner and was then ground and prepared for use as an SPE sorbent by packing it into SPE cartridges. These cartridges were used to clean up extracts of diazepam and other benzodiazepine drugs made from hair samples via a molecularly imprinted solid-phase extraction (MISPE) protocol. The MISPE method was also found to be applicable to the analysis of diazepam metabolites and other benzodiazepine drugs in addition to diazepam itself. The application of the extraction method to post-mortem hair samples yielded results that were in good agreement with ELISA data (from blood samples) and data arising from the analysis of the same blood samples using a validated in-house SPE-LC-MS-MS method. The MISPE procedure was also compared with a conventional SPE method for analysis of benzodiazepines in hair samples. The results from MISPE protocol showed better selectivity, specificity and accuracy toward diazepam (template molecule) and other benzodiazepines that display a similar resemblance to diazepam in terms of molecular structure. The MISPE procedure was found to be simpler and to offer cleaner extracts compared to a conventional SPE method.

Made available in DSpace on 2014-06-11T19:35:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12-09Bitstream added on 2014-06-13T18:47:12Z : No. of bitstreams: 1 gomes_l_dr_rcla.pdf: 1800817 bytes, checksum: b147909c9c97547974e7c7d4384c057e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Um dos principais propósitos da investigação de fenômenos em qualquer área de atuação é encontrar uma forma adequada de representação dos processos envolvidos que seja o mais simples possível. O estudo da auto-organização em agregados de organismos biológicos não pode fugir a este propósito, e foi realizado aqui em três etapas: experimentação, modelagem e validação. A experimentação vai permitir definir claramente os padrões de comportamento a serem analisados e interpretados. A modelagem irá recorrer a estratégias espaço-temporais para a síntese de explanações matemáticas, para as interações e modos de agir dos organismos. Finalmente, a validação estará baseada em simulações computacionais, comparações com os resultados experimentais e interpretação paramétrica dos modelos resultantes. Foi predominante junto ao processo de modelagem o uso apenas das informações provenientes das observações realizadas e dados experimentais coletados, caracterizando uma abordagem de modelagem bottom-up, em detrimento da incorporação de hipóteses intuitivas a respeito dos mecanismos envolvidos, procedimento típico das abordagens top-down. Além disso, a acurácia do modelo em reproduzir resultados experimentais não foi o único e principal fator de avaliação da qualidade dos modelos resultantes, pois o aspecto mais importante a ser considerado junto aos modelos é a capacidade de ampliar o conhecimento acerca do fenômeno envolvido. Embora existam muitas manifestações de auto-organização na natureza e que poderiam ser tomadas como casos de estudo, este projeto se propôs a investigar o processo de dispersão larval pós-alimentar em moscas-varejeiras do gênero Chrysomya. Essas moscas foram introduzidas no Brasil em meados dos anos 70, e são de considerável importância médico-sanitária... / In any area of investigation, one of the main goals is to identify the simplest and most adequate representation of the phenomenon being studied. The study of selforganization in aggregates of organisms is no exception to this rule. In the work described here, we used a combination of laboratory experiments, modeling and validation to clearly identify patterns of behavior. For modeling, spatiotemporal strategies were used to develop mathematical explanations of the interactions and ways organisms act. The final validation was based on computer simulations, comparisons with experimental results and parametric interpretation of the resulting models. The modeling was based on observations and data collected during the experiments, an approach known as bottom-up modeling, and which contrasts with top-down modeling that depends on the incorporation of intuitive hypotheses about the mechanisms involved. Apart from the accuracy of the model in reproducing the experimental results, the most important aspect to be considered is the ability of the resulting model(s) to increase our knowledge about a given phenomenon. In this investigation, we used postfeeding larval dispersal in blowflies of the genus Chrysomya as a model to study self-organization. Chrysomya blowflies were introduced into Brazil in the mid-1970s, and are of considerable medicosanitary importance since they are vectors of enteropathogens that cause facultative myiasis in animals and man; these flies are also used in forensic studies to estimate the postmortem interval (PMI) in humans. The larval stage in these flies is the principal period in which there is competition for discrete, ephemeral food resources in the wild. After exhaustion of the food resources, the larvae leave the food... (Complete abstract, click electronic address below)