Using Optimal Foraging Theory to Analyze the Spatial Moving Patterns of Serial Burglars

In the last decades, a novel theory was introduced to the geography of crime, called optimal foraging theory. This theory explains repeat victimization and "near repeat" victimization well, which are major concerns in the geography of crime. It assumes that the moving behavior of serial offenders is composed of two types of movement: foraging and searching. However, to date the moving behavior of serial offenders has not been well investigated. Therefore, this study was aimed at identifying the frequency and the spatial scale of these two different inter-crime movements. We designed a grid-based transition probability matrix to record the moving behavior of 31 serial burglars in Taipei Metropolis. For further analysis and comparison, an index was created to represent moving characteristics ─ the Behavior Index. In order to understand the moving behavior thoroughly, we conducted simulations with different moving behaviors and found the corresponding moving behavior of real burglars. This study found that there was an 80% chance that a serial burglar in Taipei would commit a subsequent offence within a 2.4-km radius of the former event, which indicates a general pattern of more searching. However, as we adjusted the definition of foraging, the frequency between foraging and searching also changed. The frequency depended to some extent on the definition of the spatial scale. This study also found that the Behavior Index is correlated with the commuting characteristic on Journey to Crime of burglars. When the commuting characteristic of burglars is stronger, the corresponded Behavior Index was significantly lower. This study can improve the current knowledge about the moving behavior of serial offenders and can inform strategies for preventing and predicting crimes.Table of Contents 摘要 i Abstract iii Table of Contents v List of Figures vii List of Tables viii Chapter 1 - Introduction 1 1.1 Geography of crime and its recent concerns 1 1.2 Repeat victimization and near repeat victimization 4 1.3 The optimal foraging theory 7 1.4 Objectives of the study 10 Chapter 2 - Literature review 12 2.1 Related studies of the near repeat victimization 12 2.2 Moving properties of individual offenders 18 2.3 Summary 21 Chapter 3 - Study Area and Empirical Data 23 3.1 Empirical data 23 3.2 Study area 23 Chapter 4 - Methodology 25 4.1 Recording moving behavior with transition probability matrix 26 4.1.1 Covering the study area with grids 29 4.1.2 Defining the states of grids 29 4.1.3 Recording the transition probability matrices 31 4.2 Calculating the Behavior Index 33 4.3 Simulation with different Moving Indices 36 4.4 Obtaining the Moving Index of real burglars 38 4.5 Interpreting the importance of spatial scales 41 4.6 Grouping with previous studies 42 Chapter 5 - Results 45 5.1 The Behavior Index of real burglars 45 5.1.1 Index in initial spatial scale 45 5.1.2 Indices in different spatial scales 48 5.2 The Behavior Indices of simulation 50 5.2.1 The indices of simulation in initial spatial scale 50 5.2.2 The Behavior Indices with different spatial scales 51 5.3 The Moving Index of real burglars 54 5.4 Searching Efficiency in different spatial scales 54 5.5 The Behavior Index from different groups 55 Chapter 6 - Discussion 58 6.1 The probability between long and short 58 6.2 The moving scale of serial offenders 59 6.3 The prediction and prevention of serial offenders 60 6.4 Limitations and suggestions 62 Chapter 7 - Conclusion 66 References 6