THE POLICE NATIONAL COMPUTER AND THE OFFENDERS INDEX: CAN THEY BE COMBINED FOR RESEARCH PURPOSES? Brian Francis Paul Crosland Centre for Applied Statistics, Institute of Criminology, Lancaster University Cambridge University The views expressed in this document are those of the authors, not necessarily those of the Home Office (nor do they reflect Government policy). 2 Contents Executive Summary ..................................................................................................................................... 4 i) Report Recommendations........................................................................................................................ 7 1. Introduction........................................................................................................................................... 10 1.1 Background to the research................................................................................................................................10 1.2 Definitional issues..............................................................................................................................................11 1.3 The research project ...........................................................................................................................................11 2. The research design............................................................................................................................... 14 2.1 Models of how records are retrieved..................................................................................................................14 2.2 Offences, court cases and the supply of data to the PNC and the Offenders Index............................................18 3. The PNC data ........................................................................................................................................ 21 3.1 PNC file levels ....................................................................................................................................................21 3.2 Stage 1: Obtaining PNCIDs from personal information.....................................................................................22 3.3 Stage 2. Obtaining PITO data from PNCIDs ....................................................................................................23 3.4 PNC data quality and timeliness ........................................................................................................................24 3.5. Back record conversion.....................................................................................................................................25 3.6 Advantages and disadvantages of the PNC........................................................................................................26 4. Offenders Index data ............................................................................................................................ 27 4.1 The OI database..................................................................................................................................................27 4.2 The RDS retrieval of OI data .............................................................................................................................27 4.3 Known issues with the Offenders Index.............................................................................................................28 4.4 Recommendations regarding OI data .................................................................................................................29 4.5 Advantages and disadvantages of the OI............................................................................................................29 5. The problem of offence and disposal coding....................................................................................... 30 5.1 Offence coding...................................................................................................................................................30 5.2 Disposal codes....................................................................................................................................................31 6. The research studies.............................................................................................................................. 32 6.1 Persistent Young Offenders ...............................................................................................................................32 6.2 Pathfinder...........................................................................................................................................................34 6.3 Strategic Alliance ...............................................................................................................................................35 6.4 Home Detention Curfew ....................................................................................................................................35 6.5 Sentencing Sample .............................................................................................................................................36 7. Preparing data for matching................................................................................................................ 37 7.1 Introduction........................................................................................................................................................37 7.2 Producing a composite file at the level of the individual ...................................................................................37 7.3 Levelling the court-level datasets.......................................................................................................................37 8. The matching process............................................................................................................................ 40 8.1 Matching individuals..........................................................................................................................................40 8.2 Matching court dates within individuals. ...........................................................................................................41 8.3 Matching within court dates...............................................................................................................................41 9. Example matches................................................................................................................................... 42 9.1 Case 12 Pathfinder Teesside .............................................................................................................................42 9.2 Case 253 Pathfinder: Hereford and Worcester...................................................................................................44 9.3 Case 509 Sentencing Sample ..............................................................................................................................45 9.4 Case 1445 HDC..................................................................................................................................................47 9.5 Case1146 HDC...................................................................................................................................................48 9.6 Case 1 PYO........................................................................................................................................................50 10. The results from the datasets ............................................................................................................. 51 10.1 The matching process.......................................................................................................................................51 10.2 Matching at the individual level.......................................................................................................................51 10.3 Matching at the court date level .......................................................................................................................52 11. Practical issues of hybridisation......................................................................................................... 59 11.1 What PNC records should be included on the OI?............................................................................................59 3 11.2 Specification of the hybridised record...............................................................................................................59 12. Exploration of the effect of hybridisation on a reconviction study................................................. 66 13. Implications for reconviction research.............................................................................................. 69 13.1 Timeliness and completeness of reconviction studies......................................................................................69 13.2 Auditing each data source from the other?.......................................................................................................70 13.3 Hybridisation models and updating of records.................................................................................................70 13.4 Pseudo-reconvictions .......................................................................................................................................70 13.5 Recalibrating