As investigators we are often asked to assess the credibility of a witness: it’s the client question I most dislike.

As an investigator with a background in psychology and witness memory, I am far more interested in the reliability of their evidence. It is true, for example, that the drinking habits of a witness may have a bearing on their reliability in some circumstances. The frequency of their contact with police may also influence them in one direction or another.

But the question is hardly ever as simple as it seems. It’s not as if investigators have some special power to determine the reliability of a witness. The only way to come as close to possible to finding the answer is to conduct a thorough investigation.

An investigator needs to assess carefully the possible influences at work on a witness, including social and psychological factors. And there are potentially quite a few of them.

A recent discussion on LinkedIn produced this excellent list of issues to consider when determining the credibility of a witness. I thought it was worthy of sharing in this blog post.

The credibility of a witness is determined in part by:

  • the internal consistency of her/his testimony, and possible self-contradiction,
  • whether it is true,
  • the history/reputation/character of the witness,
  • his/her motivation to lie,
  • any relation of the witness to the respondent or defendant,
  • any other conflicts of interest,
  • whether the person is testifying without duress,
  • whether the person makes statements against self-interest,
  • falsifiability of statements,
  • whether other witness testimony supports the witness’s testimony,
  • the witness’s proximity to the alleged event in time and place,
  • any cognitive impairments,
  • the language ability of the witness,
  • correct orientation as to time/place/circumstance,
  • differences and similarities to previous testimony,
  • rote or repeated nature of testimony to other witness’s testimony (which may speak to preparation or advice or coercion by a third party),
  • is the level of detail provided appropriate to the nature of the circumstances,
  • corroboration of witness testimony,
  • biased statements by the witness.

(Marc Brenman – LinkedIn comments 10 July 2013,

The point is this: assessing witness credibility involves an investigation, and the analysis of a lot of information – and that takes time and effort.

Content retrieved from: