Credibility and prior inconsistent statements 

Every witness who gives evidence puts their credibility in issue in a general sense. But the uniform Evidence Acts draw a sharp line between evidence that helps prove a fact in issue and evidence that goes only to whether a witness should be believed, and they largely exclude the second category.

The credibility rule

Section 102¹ states the rule in a single line: credibility evidence about a witness is not admissible.

Credibility evidence is evidence relevant only because it affects the assessment of a witness's credibility, and not relevant for any other purpose — or relevant for another purpose but inadmissible for that purpose.

The rationale is control of the trial. Without the rule, every witness could be examined on their entire history, and the proceeding would fragment into satellite disputes about matters that do not advance the issues.

The consequence is that credibility evidence is admissible only through an exception. An answer must identify the exception; it is not enough to say the evidence is relevant to credit.

Dual relevance

Evidence that is relevant both to credibility and to a fact in issue is not caught by the rule at all, because it is not relevant "only" to credibility. It is admitted subject to the ordinary rules — hearsay, opinion, tendency — and may then be used for both purposes, subject to any limiting direction.

This is where careful analysis pays. A prior inconsistent statement, once admitted, is under the uniform Acts evidence of the truth of its contents as well as evidence undermining the witness, because the hearsay rule does not apply to a prior statement of a witness who is available and has been examined about it. That is a significant departure from the common law position, where such statements went to credit alone.

Cross-examination as to credibility

The principal exception permits cross-examination on credibility, but only where the evidence could substantially affect the assessment of the credibility of the witness (s 103(1)). Get the words right: s 103 was amended to this form, and the older "substantial probative value" wording is still the test under ss 97 and 98 for tendency and coincidence — quoting it here is a common slip that imports the wrong provision's threshold. In assessing that, the court considers matters including whether the evidence tends to prove the witness knowingly or recklessly made a false representation while under an obligation to tell the truth, and the period that has elapsed since the events.

Additional restrictions apply:

• Leave is required to cross-examine a defendant in a criminal proceeding about credibility, and the statutory conditions are narrow.
• Cross-examination must not be improper — misleading, unduly annoying, harassing, intimidating, offensive, oppressive, or put in a manner or tone belittling to the witness. The court has a duty to disallow such questions, and specific protections apply to vulnerable witnesses.

Prior inconsistent statements

A prior inconsistent statement is one the witness made earlier that is inconsistent with their evidence. Section 43² governs the procedure:

1. The cross-examiner need not first show the document to the witness or disclose its contents.
2. But before other evidence of the statement may be adduced, the witness must have been told enough of the circumstances of the statement to identify it, and must have been given an opportunity to admit or deny making it.
3. If the witness denies or does not admit making the statement, evidence of it may then be led from another source.

The rule is one of fairness: a witness should have the chance to explain or deny before being contradicted.

The finality rule and its exceptions

The general position is that a cross-examiner is bound by the answer given on a collateral credibility matter — they may not call evidence to contradict it. Without this, trials would extend indefinitely.

Section 106 provides exceptions. Where the witness has denied the substance of the evidence, and the court gives leave (or the matter falls within a listed category), evidence may be adduced to rebut the denial. The listed categories include that the witness:

• is biased or has a motive to be untruthful;
• has been convicted of an offence, including one of dishonesty;
• has made a prior inconsistent statement;
• is or was unable to be aware of matters they gave evidence about; or
• has knowingly or recklessly made a false representation while under an obligation to tell the truth.

For the first three and the last of those, leave is not required.

Re-establishing credibility

Once credibility has been attacked, evidence may be admitted to re-establish it. In re-examination, the witness may explain evidence given in cross-examination. Other evidence relevant to credibility may be adduced with leave.

A prior consistent statement is generally inadmissible, but becomes admissible where it is adduced to rebut a suggestion of recent invention or of a fabricated or reconstructed account, and leave is given.

Expert evidence on credibility

Expert opinion evidence relevant to credibility is admissible in limited circumstances — where the witness has specialised knowledge of child development or of the effects of a disability, and the opinion could substantially affect the assessment of credibility. This is how evidence about counter- intuitive behaviour by complainants is received.

Applying this in a problem question

1. Ask first whether the evidence is relevant to a fact in issue. If it is, the credibility rule does not apply and you should analyse it under the ordinary rules.
2. If it is relevant only to credibility, name the exception relied on.
3. For cross-examination, ask whether the evidence could substantially affect the assessment of credibility, with reasons, and check whether leave is required.
4. For a prior inconsistent statement, walk through the s 43 procedure before considering whether other evidence may be led.
5. Address the finality rule expressly when rebuttal evidence is proposed, and identify the category.
6. Consider what use the tribunal may make of the evidence, and whether a limiting direction is needed.

Self-check

• Have I tested for dual relevance before applying the credibility rule?
• Have I named a specific exception rather than asserting relevance to credit?
• Have I checked whether leave is required?
• Have I followed the s 43 sequence before allowing contradiction?
• Have I noted that a prior inconsistent statement may be evidence of its truth under the uniform Acts?