Corroboration and Forensic Reasoning Rules

Abstract This chapter charts an evolution in common law regulatory techniques from (scattered, residual) corroboration requirements and related quantitative proof standards to an expanding modern corpus of primarily qualitative forensic reasoning rules. As an epistemic operator, ‘corroboration’ is simply supporting or convergent evidence, but English law adopted a narrower technical definition. Over the course of the twentieth century, these legal technicalities were gradually abandoned—along with most of English law’s formal requirements for ‘two witnesses’ or other corroboration stipulations (some of which were rooted in discriminatory stereotypes). The judges improvised a series of ‘corroboration warnings’, in relation to eyewitness identification evidence (Turnbull) and witnesses who, as a class, pose enhanced risks of unreliability owing to compromised capacity (Spencer) or self-interest (Beck). Such warnings were subsequently generalized (Makanjuola), and are now extensively adumbrated by the Crown Court Compendium in relation to myriad categories of ‘suspect’ evidence. The discussion draws together judicial directions examined in pervious chapters (e.g. in relation to ‘suspicious silence’), well-established common law doctrines (e.g. Lucas directions on lies), statutory warnings (e.g. PACE 1984, s.77), and post-Makanjuola judicial improvisation, into the capacious conceptual framework of ‘forensic reasoning rules’. Institutionally, this development represents a shift from categorical inadmissibility rules to qualified admissibility standards. For evidence law analysts, forensic reasoning rules afford holistic institutional insights unavailable to studies of atomistic exclusionary rules. In articulating (fragments of) the logic of inferential reasoning authoritatively communicated to fact-finders, detailed judicial directions intimate how jurors are meant to reason from evidence to proof. The general topic of corroboration has lately acquired a human rights dimension, encapsulated in the ‘Al-Khawaja saga’ over ‘sole or decisive’ evidence.