One of the real pleasures of working at a university is the thoroughfare of constant student enquiry where students challenge preconceptions about the law and its structure, its form, its provenance and its legitimacy.

This is particularly so in the context of postgraduate supervision where I have had the privilege of supervising many practitioners in the art of academic scholarship in the context of vexing questions their busy practice would otherwise give them no time to contemplate.

One such paper I recently supervised focused on demeanour evidence. As a practitioner, this particular Masters student was troubled by the value or weight given to the demeanour of witnesses when assessing credibility.

The paper he completed on the topic was outstanding, albeit very troubling in its repercussions for litigation under an adversarial system of justice.

His central contention was that the rational basis of demeanour evidence is highly questionable and that, as such, a standard warning ought to be given by judges in all cases where credibility is at issue.

Rather than replicate this student’s fine work, I would like to develop his thesis and use it to ask the altogether more troubling question of whether demeanour evidence, as an increasingly undermined concept, is now able to be viewed at all as a factor relevant to rational fact finding? Further, is the concept of demeanour so weak as to undermine many of the preconceptions our system of justice is seemingly based upon?

Heady stuff I know, particularly when you may have just picked this publication up in the tea room while enjoying a quick five minute break – but please, stay with me.

The rational foundation of demeanour evidence as a matter of legitimate consideration in the assessing of credibility has long been questioned.

In recent years, the value of demeanour evidence in assessing credibility has been all but rejected – at least by science if not law.

In a highly controlled laboratory environment it seems possible to make accurate conclusions (albeit very limited) on the truthfulness of an individual from their demeanour. The courtroom as a highly charged, intimidating, inherently confrontational and dehumanising environment is as far from such a scientifically controlled environment as one could get.

Despite this cynicism, judges have directed juries and likely still do on a daily basis, on the value of demeanour evidence. ‘Ladies and gentlemen of the jury, you have had the benefit of the witness giving evidence before you today ...’ or some such other language is, I am sure, not uncommonly heard in jury trials around New Zealand let alone taken on board by judges in judge alone fixtures (both civil and criminal).

Beyond the assessment of credibility by a fact finder, demeanour evidence has also been relevant to the question of admissibility where the demeanour of a witness has been noted pre trial and used by a judge in determining the reliability of evidence for the purposes of determining relevance and probative value.

It would be unfair to say warnings on assessing and giving weight to demeanour were ad hoc, although the New Zealand judiciary, it seems, is far from recognising the need to give a general warning in all cases on the value of demeanour. This notwithstanding, I want to pick up on two points.

First is the law’s forlorn attempt to pigeonhole demeanour as an aspect of credibility, and to therefore only be concerned with its frailties when credibility is in issue. The second is the wider repercussions of an undermining in our faith in demeanour more generally.

The issue of credibility is often not directly in issue in a case. I believe, however, that it is artificial to assume that assessments of credibility are not made by judges and juries in all cases where testimonial evidence is given. If not credibility in the “legal” sense, the demeanour of a witness will likely always be used in determining both the believability of a witness (this relating more to credibility) or the weight to be given to their testimony.

A pertinent example of this can be seen in the context of expert evidence. Expert A, for example, is a strong speaker, articulate, confident, forthright, whereas Expert B is shy, appears to lack confidence and finds it difficult to make eye contact. In light of this, it seems incongruous to suggest that demeanour is only something relevant in cases where credibility is recognised as being in issue.

Moving to the second and more troubling point, what faith can we put on the process of giving evidence in open court if the demeanour of a witness in answering questions does not present itself as a clear guide to the assessment of truth?

There are, of course, many non-epistemic reasons why evidence may still need to be given in open court – the notion of fairness inherent in the requirement that to challenge someone you ought to do so face to face is one such example, for example the right to confrontation under the United States Constitution.

However, it may be that litigators ought to be more forceful in their applications for evidence to be given in alternative ways, that the courts ought to take a less precious approach to such applications and that concepts based upon an inherent assumption of the worth of seeing a person give their evidence be revisited (hearsay for example).

Although this may seem academic, the reliance of the New Zealand courts on demeanour evidence seems not to be supported by science that suggests demeanour to be logically flawed.

For my part it seems artificial to attempt to pigeonhole the problem away from prying eyes through the classification of demeanour as only relevant when it comes to credibility.

As my Masters student suggests, it seems illogical that there not be a more general warning given.

For litigators, in the absence of such a warning you might be tempted to call expert evidence on the frailty of making such an assessment – an assessment that judges and even we are prone to make with a misplaced confidence in our ability to assess demeanour.

But separate to the ability of litigators to challenge demeanour as evidence, there appear to exist fundamental questions as to the core foundation of the adversarial process – a process intended to be based upon the rational attainment of facts.

Dr Chris Gallavin is an Associate Professor and Dean of Law at Canterbury University. He has published extensively on criminal justice and on evidence and procedure in particular. He is the author of the appellant handbook, Evidence (LexisNexis, Wellington, 2008), and regularly undertakes consultant work in the area of the law of evidence.