1. Criminal Career Research, Mathematical Models, and Testing Quantitative Predictions from Theories 1
Background 1
Blumstein and Cohen (1979) 2
The National Academy Panel 4
Explaining the Growth in Recidivism Probabilities 6
Explaining the Individual Offending Frequency 11
Objections to Criminal Career Research 14
Criminal Career Research in the Last 20 Years 17
Aims of this Book 18
Methodological Notes 20
2. An Analysis of the Offenders Index 23
Sources of Data 23
Recidivism 26
Reconviction Rate 34
Reconciling the Risk and Rate Categories 39
Gender 40
Is Criminality Constant over the Cohorts? 43
3. The Theory and a Simple Model 47
Orientation 47
Introduction 47
The Assumptions of our Theory 49
Explaining the Age-Crime Curve 50
The Rise in Crime from 10 to 17 Years of Age 56
Modelling the Age-Crime Curve 59
The 100,000 Active Prolific Offenders 68
Corollaries and Comments 70
Conclusion 73
4. Criminal Careers of Serious, Less Serious, and Trivial Offenders 75
Orientation 75
Introduction 75
Offenders with Custody at First Court Appearance 76
Custody Rates 78
Serious Offenders 79
Less Serious Offenders 81
Serious Offences 82
Simplified Modelling of Convictions for Serious Offences 83
Simplified Modelling of all Convictions 88
Versatility or Specialization in Offending 90
Trivial Offenders 98
Conclusion 105
5. Is Age the Primary Influence on Offending? 107
Orientation 107
Introduction 107
Possible Types of Age Dependence 109
Testing the Theories 111
Conclusion 119
6. Characteristics of Individuals 123
Orientation 123
Introduction 123
The Rationale and Development of OASys 124
Analysis of the Pilot OASys Data 128
The Distribution of Section 11 Scores 131
Is there Structure in the Section 11 Information in OASys? 138
Homogeneous and Heterogeneous Section 11 Questions 140
Conclusions from the OASys Pilot Data Analysis 142
Analysis of Operational OASys Data 144
Analysis of April 2004 PNC Conviction Data 149
Conclusions 154
7. Applications for Managing the Criminal Justice System 155
Orientation 155
Introduction 155
The Flow Model 156
Predicting the Prison Population 158
The DNA Database 164
Conclusion 167
8. Criminal Policy Implications 169
Orientation 169
Introduction 169
Overview of the Theory 169
The Categories 170
Areas where Policy could Influence Crime 172
Childhood Early Interventions 173
Early Career Interventions 174
Increasing the Efficiency of Conviction 175
Offender Treatment Programmes 176
Prolific and other Priority Offenders 176
Implications and Uses of the Theory 180
Frequently Asked Questions 184
9. Summary and Conclusions 187
Summary 187
The Origin of the Offender Categories 197
Criminality 198
Recidivism 199
Conviction Rate λ 200
The Effects of Formal Warnings and Cautions 201
The Criminal Career Debate 203
Conclusions 208
Appendix: Mathematical Notes 211
Introduction 211
Constant Probability Systems 212
Allocation of Offenders to the Risk/Rate Categories 215
An Alternative Modelling Approach 217
Incapacitation 219
Steady State Solutions 223
Estimating the Active Offender Population Size 226
Maximum Likelihood Estimation of the Recidivism Parameters 227
Bibliography 231
Index 243