The Use of Forensic Science in Volume Crime Investigations: a Review of the Research Literature
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The use of forensic science in volume crime investigations: a review of the research literature Sarah-Anne Bradbury Andy Feist Home Office Online Report 43/05 The views expressed in this report are those of the authors, not necessarily those of the Home Office (nor do they reflect Government policy). The use of forensic science in volume crime investigations: a review of the research literature Sarah-Anne Bradbury Andy Feist Online Report 43/05 Acknowledgements Many people helped contribute to the preparation of this study. In particular we would like to thank Mark Bangs who worked on the earlier stages of the project. Joy Curwen, Forensic Science Service, as well as individual force Scientific Support Managers, kindly submitted research studies for inclusion. Professor John Burrows and Professor Nick Tilley also assisted with the identification of key studies in the scoping stage. We would like to thank Robin Williams, University of Durham, for acting as the external assessor for this study. Sarah-Anne Bradbury, Andy Feist Sarah-Anne Bradbury and Andy Feist are members of RDS (Crime Reduction and Community Safety Group). ii Contents Acknowledgements ii Executive summary v 1. Background and method 1 Objectives of the study 1 Method 2 Approaches to forensic research 5 Structure of the report 6 2. Overview of the contribution of forensic science to police investigations 8 The contribution of forensics to the detection of crime 8 Physical evidence as corroborative evidence, a means for identifying suspects, or as an intelligence tool? 9 Accessing the actual contribution of physical evidence to the detection of volume crime cases 10 Summary 12 3. Call handling and initial response 13 Call handlers 13 Who attends crime scenes to retrieve physical evidence? 13 Decision-making about which scenes to attend 14 Screening for attendance, officer discretion and forensic awareness 15 Overall patterns of scene attendance by CSEs 17 Summary 20 4. Information and evidence gathering (1): up to the point of submission 21 The role that crime scene examiners perform 21 Rates of retrieval for physical evidence 22 Factors influencing the retrieval of forensic information 25 Submission of crime scene samples for analysis 30 Summary 33 5. Information and evidence gathering (2): post-submission 36 Achieving identifications 36 Summary 44 6. Suspect handling 46 Summary 48 7. The post-identification investigation: converting identifications into detections 49 The relationship between matches and detections 50 Identifications that do not yield detections 53 Timeliness 56 Summary 57 8. Overall attrition and the contribution of forensics to convictions 58 iii The use of forensic evidence at court 61 Summary 67 9. Awareness and communication 68 Attitudes and communications between CSEs and investigating officers 69 Summary 70 10. Summary and conclusions 71 Initial response and crime scene attendance 72 Retrieval of forensic material 72 Submissions and identifications 74 Suspect handling 74 Converting identifications to detections 74 Overall attrition and conviction 75 Communication and integration 75 Crime reduction impacts and cost effectiveness 76 Where the evidence base can be further developed 77 Appendix 1. Search terms 78 Appendix 2. Selected studies (summaries) 80 References 88 iv Executive summary The use of forensic science techniques has traditionally been concentrated on more serious crimes such as rape and homicide. Increasingly, however, forensic techniques are being used routinely to aid the investigation of volume crimes such as burglary and vehicle crime. The current study aims to draw together UK and international social reseach on the application of forensic techniques to volume crime investigations. The main objectives of the review were to: • identify the mechanisms by which forensic science is applied to the investigation of volume crime; • identify the strengths and weaknesses of the use of forensics in the investigation of volume crime; and, • identify the way in which forensic science contributes to the effective and efficient detection (and conviction) of crime. Overview of the contribution of forensic science to police investigations A number of general themes emerge from the research literature in terms of the overall contribution that forensics makes to crime detection. • The proportion of volume crime offences detected through the use of forensic evidence has, historically, been low (less than 10 per cent of all detections). However, the growth of automated searching, alongside new forensic techniques such as DNA, and initiatives to improve attendance rates have increased the proportion of volume crime offences detected using forensic evidence. In the UK, it is estimated that, for directly detected volume crimes, the main evidence securing the detection was forensic in more than one quarter of cases. • Traditionally forensic evidence has been used principally to ‘corroborate’ evidence against known offenders; increasingly, however, forensic material is being used in a way that identifies unknown offenders. • The presence of forensic material greatly increases the odds of detection where other types of evidence are not available. Overall, therefore, forensic material makes the greatest contribution to detecting harder-to-solve crimes. Initial response and crime scene attendance • The use of dedicated Crime Scene Examiners (CSEs) is not universal. In the US, responsibility for collecting forensic evidence from crime scenes is often shared amongst CSEs, investigators or patrol officers. Policies about the deployment of CSEs range from blanket attendance for certain crime types, to discretionary attendance on the basis of information provided to a call taker, or by first attending officers (FAOs). In England and Wales, burglary dwelling attendance rates are generally high1, while a smaller proportion of vehicle crime offences are attended. • For offences where attendance is discretionary, decisions to send a CSE will be influenced primarily by the potential to recover forensic material and the perceived seriousness of the offence. Research into FAO decision-making over scene attendance 1 Currently estimated to be around 85 per cent (2004/05). v has highlighted potential weaknesses in this method of CSE deployment, especially low levels of forensic awareness amongst FAOs. Even where mandatory attendance policies exist, the actual pattern of attendance may fall below what is expected either due to poor communication or the reluctance of patrol officers to be directed to meet mandatory instructions for CSE attendance. • A recurring theme in this aspect of forensic activity is that of police force variations in crime scene attendance rates (even allowing for similar crime types). Resourcing and geography have been identified as important factors in determining levels of CSE visits. One study of forensic performance in English and Welsh forces noted that, while the greater number of CSEs per recorded crime was generally associated with higher proportions of all scenes attended, not all forces conformed to the expected pattern. Other factors might limit attendance levels (e.g. less densely populated rural forces entailing greater distances between scene visits). The retrieval of forensic material • Only one study was identified that had involved observing what crime scene examiners do at scenes, and how they fit into the broader investigative process. In the US police department studied, CSEs were found to be disjointed members of an investigative team, fitting uncomfortably into the more rank-based structure of mainstream policing. The work of individual CSEs was poorly quality controlled: investigation reports, the main assessment tool for individual CSE performance, were found to be rarely reviewed. Victims’ perceptions of the service provided by the CSE were generally positive and this was generally acknowledged by CSEs themselves as an important part of their wider role. Other studies have, however, found victims to be critical of ill-considered CSE examinations. • The initial screening of offences for forensic examination makes it hard to establish genuine base rates for the potential to retrieve forensic material from crime scenes. A study which involved attendance by forensic specialists at unscreened major felony crime scenes found that fingermarks were present at similar proportions of burglary dwelling and vehicle crimes (41%), and 45 per cent of non-residential burglaries. The failure of scenes to yield physical evidence was usually due to scenes being cleaned prior to CSE attendance, inaccessible scenes, or minimal disturbance by the offender. • Most studies of forensic retrieval rates at burglaries have consistently identified fingermarks as the most frequently retrieved contact trace material, with typically just under one in three residential burglary scenes attended resulting in the retrieval of fingerprints. Data on English and Welsh retrieval rates put DNA retrieval at ten per cent of all scenes visited (similar to shoemarks, although these recorded a greater variation between forces). Relatively high retrieval rates per crime scene visited are generally associated with crimes which are more frequently subjected to selective CSE attendance (screening), such as vehicle crime. Retrieval rates for offences receiving high levels of attendance (such as burglary dwelling) are, by comparison, generally lower. • Even when comparing rates for particular material within particular crime types, marked area by area variations