Evaluation of scientific findings in forensic science
Franco Taroni, Alex Biedermann, Silvia Bozza, Paolo Garbolino, Colin G. G. Aitken · 2014
Theory, methods and applications of probability and statistics underlie the evaluation of scientific evidence. Forensic scientists should give the courts an evaluation that adequately illustrates the convincing force of their results. This chapter proposes a summary of the probabilistic approach based on Bayes' theorem and the use of the likelihood ratio for the assessment of the probative value of scientific findings. Formulae for likelihood ratios are developed and presented with a particular emphasis on the context of the case under examination and by relying on the concept of the ‘hierarchy of propositions’. It is now widely accepted that the coherent and balanced assessment of scientific findings requires forensic scientists to consider competing propositions that typically represent alternatives proposed by the prosecution and the defence to illustrate their view of the case under examination.