Evidence in court: witness preparation and cross-examination style effects on adult witness accuracy.

Witnesses play a clear and pivotal role in the criminal justice system and there is an obvious public interest in identifying procedures that both undermine and maximize the quality of evidence received by the criminal courts. This paper reports an investigation into the effects of witness familiarization and cross-examination type on adult witness accuracy that situates outcomes in both legal and psychological context. 60 mock witnesses observed a crime event and each witness was then cross-examined by a practising barrister in a moot courtroom according to two conditions - either via a scripted complex version of cross-examination or by a simpler but equivalent scripted examination. Mock witnesses were also allocated to two further conditions - half the participants received a guidance booklet on cross-examination and the other half received no familiarization to the process. Study outcomes showed that familiarization of witnesses to cross-examination processes increased accurate responses and reduced errors. The guidance seemingly allowed accessibility to cognitive information that enabled witnesses to process information more effectively. On this basis, advance written information about the nature of the cross-examination and potentially misleading tactics used by advocates could help to immunize against negative lawyerly influence.