The development of Case Assessment and Interpretation (CAI) in forensic science

  • Graham Jackson

    Student thesis: Doctoral Thesis


    Expert opinion has been, and still is, of undoubted assistance in the investigation of crime and the administration of criminal justice. It has also been the cause of a number of celebrated miscarriages of justice. Technological advances and greater investment in forensic science resources in the latter half of the 20 century meant that forensic science could be applied to many more cases than ever before. It also meant that forensic scientists had to meet new challenges in the way they formed and expressed opinions about their findings. The creation of a commercial market for forensic science in the 1990s in England and Wales put additional pressures on suppliers to provide value-for-money for their customers.

    In an attempt to satisfy the potentially conflicting demands of providing robust, reliable opinion and of giving value-for-money, a novel process called Case Assessment and Interpretation (CAI), based on the underlying logic of Bayes Theorem and the use of likelihood ratios, was proposed in 1998 as a model of good practice in forensic science. Over the course of the next 12 years, the model process was applied to most main-stream forensic science disciplines and, as a result, the ideas were refined and fresh insights on the nature of expertise were gained.

    This thesis describes the background to the initial development of the CAI model, sets out subsequent improvements, demonstrates how the model may have helped avoid misleading opinion being given and considers the current status of CAI. The conclusion of the thesis is that assessment of likelihood ratios, within the framework of the Case Assessment and Interpretation model, does provide a philosophical, yet practical, means of delivering robust, reliable opinion and value-for-money.
    Date of AwardMay 2011
    Original languageEnglish
    SupervisorDavid H. Bremner (Supervisor)

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