Voir dire 

A voir dire is a hearing within a hearing: a trial of a preliminary question on which the admissibility of evidence, or the competence of a witness, depends. It is often described as a trial within a trial, and in a jury trial it is conducted with the jury absent.

When a voir dire is held

The court holds a voir dire where a factual question must be resolved before evidence can be admitted, and where the answer cannot simply be assumed. Typical occasions include:

• Confessional evidence, where it is contended that an admission was not made voluntarily, or was influenced by violent, oppressive, inhuman or degrading conduct, or by a threat of such conduct.
• Improperly or illegally obtained evidence, where the facts of the obtaining are in dispute and the court must decide whether to exercise the discretion to exclude.
• Expert evidence, where the existence of specialised knowledge, or the basis of the opinion, is challenged.
• Competence and compellability, where a witness's capacity to give sworn or unsworn evidence is in question.
• Identification evidence, where the circumstances of an identification parade or photo board are disputed.

Not every objection requires a voir dire. Where the question can be decided on the face of the material, or on submissions, the court will decide it without hearing evidence.

Conducting the voir dire

The party seeking to adduce the evidence usually bears the onus on the preliminary question, and the standard is the balance of probabilities. Evidence is called and witnesses may be cross-examined in the ordinary way.

Two features distinguish it:

• The rules of evidence may be relaxed. On a preliminary question the court is not bound by the ordinary rules in the same way, because the question is one of admissibility rather than of the facts in issue.
• Where the question concerns whether a defendant's admission was influenced by violent or oppressive conduct, the hearing must be held in the jury's absence. In other cases it is a matter for the court, though it will almost always be held without the jury where the evidence would prejudice them if the objection succeeds.

Use of the defendant's evidence

A defendant may need to give evidence on the voir dire — for instance, to describe what happened in the interview room. The statute protects them: evidence given by a defendant on a voir dire is not admissible against them in the trial proper, except in a prosecution for giving false evidence. In the uniform jurisdictions that protection is s 189 of the Evidence Act 1995 (Cth) and its state equivalents.¹

Without this protection the voir dire would be a trap, forcing the defendant to choose between contesting admissibility and preserving the right not to give evidence.

The outcome

If the objection succeeds, the evidence is excluded and the jury never hears it. If it fails, the evidence is led in the trial proper — and the same witnesses may be called again before the jury, since what happened on the voir dire is not evidence in the trial.

A ruling on a voir dire is not final in the sense that the trial judge may revisit it if the evidentiary position changes. The jury may also be invited to consider, as a matter of weight, the same circumstances that were argued on admissibility — a confession ruled admissible may still be attacked before the jury as unreliable.

Applying this in a problem question

1. Identify the preliminary question precisely, and the provision or discretion that makes it decisive.
2. Say who bears the onus and to what standard.
3. Address whether the jury must be absent, distinguishing the mandatory case from the discretionary one.
4. Note the protection attaching to a defendant's evidence if the facts raise it.
5. Separate admissibility from weight — the same facts often go to both.

Self-check

• Have I identified the specific preliminary question rather than the general objection?
• Have I allocated the onus?
• Have I checked whether the jury's absence is mandatory?
• Have I kept admissibility and weight distinct?