First of three articles directed to effective advocacy by reviewing court methods of assessing testimony. This month: evaluating credibility

Understanding how summary criminal courts reach verdicts can help advocates to develop rapport with the bench, avoid unproductive tactics and focus on significant matters. But neither legal training nor legal literature provides this insight. The assessment of testimony is seen as just a commonsense process which needs neither analysis nor training for court lawyers or the judiciary. However trial and error experience of advocacy would be enhanced by systematic study of the complex ways in which facts are proved.

How the law helps

Legal procedures do not favour either party. They are intended to help courts to reach correct verdicts. In cross-examination the adversarial trial structure lets parties highlight, challenge and dissect every contested point. Rules of evidence exclude unreliable forms of testimony. The oath, affirmation and penalties are deterrents to offences involving deception. Innocence is presumed. For conviction evidence must be corroborated, the prosecution has the burden of proof, and guilt must be proved beyond reasonable doubt. Such measures contribute to proper outcomes, subject of course to a court’s judgment.

Facts not proved by witnesses

Inferences from circumstantial evidence or conclusions derived from real or documentary evidence transcend introductory testimony. In circumstantial evidence, typically, each witness speaks to a single fact which, even if it is true, would not establish guilt by itself. However a court can go further by drawing an inference of guilt from the totality of these facts and their relationship to each other. This is entirely a judicial process. It is not testimony.

Similarly, real or documentary evidence such as a knife or a receipt requires the testimony of witnesses when it is produced, but it is then for the court, not these witnesses, to reach conclusions derived from that evidence.

Judicial knowledge, presumptions, formal admissions and informal concessions are not conclusions about testimony. These approaches help courts to decide other disputed facts.

The issue: crime or identity?

While for conviction the prosecution must prove both the commission of the crime and the accused’s responsibility for it, in practice, for sound reasons, the defence can usually oppose only one of these contentions. They rarely admit the undisputed issue by formal procedure, but inevitably their lack of opposition emerges and allows the prosecution to prove that branch of their case easily. If so the court, in effect, only needs to decide whether the crime was committed, or whether the accused was the offender, but not both questions.

Why is any testimony believed?

Many forms of deception are attempted in criminal trials, including falsely asserting or denying facts, testifying reluctantly or evasively, and falsely qualifying true reports in order to distort them. Sometimes fear of reprisals, or collusion between witnesses, plays a part.

The nature of belief and how it is formed are questions for psychologists. For lawyers two essentials for belief are that:

  • the witness must be trusted; and
  • the quality of his or her evidence must be acceptable.

These criteria interact and are difficult to separate. Both must be met. If a trusted witness gives unreasonable evidence he/she may be thought to be mistaken. Again, even an impeccable report may be disbelieved if the witness is distrusted. Trust is a human response of the bench to witnesses as persons, arising from perceptions of their personal aspects and what they say. These personal aspects will now be considered.


Traditionally it has been thought that a witness’s demeanour can guide a court in deciding whether or not he/she is lying. Demeanour consists of everything about a witness which is seen or heard when he/she testifies – excluding the content of the evidence. It includes both voluntary signs like posture or rate of speech and involuntary signs like blushing or trembling.

However according to leading psychologists, after decades of intensive research, demeanour per se is not a reliable guide to detecting lies or truth. Their conclusion is that there are no specific or identifiable signs of lying in a person’s demeanour. Judicial experience has led distinguished judges to the same view.

It has to be accepted that assessing demeanour is not a quick fix for judicial lie-detection. Being on the bench is not a licence to guess. However demeanour is not meaningless. People show their feelings – although not whether or not they are lying – by identifiable bodily and vocal signs as part of human non-verbal communication and interaction. The court perceives this as part of the whole picture.

If a witness appears to be anxious there could be many reasons for this like concern about testifying, being mistaken, the outcome, or reprisals. Yet he/she could be telling the truth.

Courts are expected to reach their verdicts by weighing the whole of the evidence rather than by forming an impression of any single witness’s honesty – although this may contribute to the overall judgment. Inevitably an impression of one witness in isolation is subjective and lacks the precision of rocket science.

Personality and character

Personality is the assembly of features which constitute individuality. Character is the moral aspect of personality. Usually courts only gain limited information and surface impressions of the personalities and characters of witnesses.

In isolation this may not be a sound basis for believing or disbelieving testimony. Life experience suggests that it is not cynical to suppose that almost any kind of person may be truthful or untruthful depending on the circumstances. If so, witnesses cannot be divided into categories of those who are credible and those who are not.

Feelings and motives

Feelings need no explanation. When a witness’s feelings are displayed in his/her demeanour or testimony, this may either support or detract from its credibility. For example, a victim’s hostility to the accused may be regarded as reinforcing her identification evidence.

Motives are states of arousal which determine purposive behaviour. The bench can usually detect the motives of witnesses who have some interest in the outcome. But sometimes apparently independent witnesses may have unsuspected personal reasons for giving biased or false testimony. It is unsound to disbelieve testimony merely because a witness is motivated in giving it. On that view, for example, all testimony given by accused persons would be discredited. But the court’s perception of witnesses’ motives may affect the weight attributed to their testimony.

Feelings and motives may be perceived in testimony apart from observing and listening to witnesses. As a result of normal, direct human perception, courts may understand witnesses’ emotional states such as anxiety, anger, grief or embarrassment. But to detect motives, courts also consider a witness’s interest in the outcome and the content of his/her testimony. For example, suspicion about lying or bias may be aroused when everything a witness says points dogmatically in one direction, whereas in real life situations there are often uncertainties, gaps or conflicting elements which point in opposite directions.

Such subtle ways of evaluating testimony may not be conclusive in themselves, but they may be enough to put a court on its guard.

Quality of the evidence

Sound judgments about the credibility of evidence also depend on analysis of its content. Evidence which contains contradictions, inconsistencies, impossibilities or improbabilities is less credible. Conversely, agreed facts and realistic stories are more likely to be accepted.

    Contradiction and inconsistency. The intended conflict between the adversaries’ stories is best described as contradiction. Often, by itself, either version might be plausible. But inconsistency denotes unintended, internal differences about significant facts in the evidence of one or more witnesses who support the same story. If they must know the real facts the court may conclude that someone is lying, not mistaken. If so, all or part of the inconsistent evidence, and even consistent evidence, from these sources may be rejected. However, minor differences between eyewitnesses often arise from the normal fallibility of observation and memory rather than lying. Also, too much consistency, especially about details, in the evidence of several witnesses who support the same story may sometimes suggest collusion and falsehood.

Impossibility and improbability. Lies which describe impossible facts are uncommon in examination-in-chief, since their falsity would be obvious. But the impossibility of what a witness says may emerge when in cross-examination it is compared with other accepted facts. The conclusion may be that a witness who must know the real facts and who states something impossible is lying.

Turning to probability, for a conviction the prosecution must prove guilt beyond reasonable doubt. Even a high degree of probability will not suffice. This standard of proof refers to the verdict which is the court’s overall judgment based on the cumulative weight of the whole of the evidence. It applies to proof of the main issues, namely that the crime was committed and that it was committed by the accused. However, probability may be enough to establish some secondary facts or those where the defence has a burden of proof.

In probability judgments the bench applies the test of experience of life. Probability is a matter of degree but it cannot be quantified in the area of court decisions. The subjectivity of such judgments is unavoidable. The credibility of any testimony may be diminished or destroyed if the court decides that it is improbable. If the witness must know the real facts the conclusion would be that he/she is lying, not mistaken.

The legal context in which facts are decided and how the assessment of credibility is based on perceptions of witnesses and analysis of their testimony have been outlined. The second article will consider the reliability of observation, memory and eyewitness testimony. The third will discuss the role of advocacy and how courts form their overall judgments by weighing the whole of the evidence.

Marcus Stone, a sheriff for 25 years and now a mediator, is the author of several books on deciding facts in courts and advocacy. He is now writing another book entitled Deciding the Facts in Summary Criminal Trials. e:


The process of assessing the credibility of disputed police evidence illustrates some features of judicial decisions.

The demeanour and apparent character of police witnesses are hardly conclusive. Police witnesses often make a good impression. Ascertaining the witnesses’ motives is the key to evaluating them as persons who can or cannot be trusted.

Defence cross-examiners (possibly supported by their witnesses) may accuse police of wrongful zeal for a conviction or support for colleagues, desire for promotion, or malice, which has caused them to lie. Whether true or false, these allegations will be firmly denied.

Courts may weigh the probability of such misconduct against the risks and possible consequences like disgrace, prosecution, imprisonment, and loss of career and pension. If police testimony is false, this may either be apparent to other officers, or undetectable.

It could be difficult to decide whether police witnesses were lying from psychological considerations in isolation. But courts do not do so. They analyse, compare and weigh the whole of the evidence relating to the essential issues. This may establish some facts positively and expose any inconsistent, improbable and unacceptable evidence, resulting in either proof of guilt beyond reasonable doubt, or acquittal. The credibility of any part of the evidence should be decided in the whole context; it is the tributary not the river.

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