Admissibility Versus Weight: A Critical Distinction

The Two Questions

Every piece of evidence in a criminal trial raises two distinct questions:

1. Admissibility: Should this evidence be received at all? This is a question of law, determined by the judge (or magistrate in summary proceedings).
2. Weight: If admissible, how much reliance should the tribunal of fact place on this evidence? This is a question of fact, determined by the jury (or magistrate).

These questions are analytically distinct. Evidence may satisfy admissibility requirements while deserving minimal weight. Conversely, highly probative evidence may be excluded on admissibility grounds despite its apparent reliability.

Admissibility: The Gatekeeping Function

The admissibility rules serve a gatekeeping function, determining what evidence the tribunal of fact will be permitted to consider. The Evidence Act 1995 (NSW) establishes the framework for these determinations.

The Fundamental Rule

Section 56 establishes the fundamental rule: evidence that is relevant is admissible, subject to the exclusionary rules in the Act. Relevance is a low threshold — evidence is relevant if it could rationally affect the assessment of a fact in issue.

Exclusionary Rules

The Evidence Act contains numerous exclusionary rules that may render otherwise relevant evidence inadmissible:

• Hearsay rule (Part 3.2): Evidence of previous representations offered to prove the truth of those representations
• Opinion rule (Part 3.3): Evidence of opinions, except expert opinion in defined circumstances
• Tendency and coincidence (Part 3.6): Evidence of character or tendency, subject to leave requirements
• Credibility rule (Part 3.7): Evidence relevant only to credibility, subject to exceptions
• Privilege (Part 3.10): Legal professional privilege, privilege against self-incrimination

Discretionary Exclusions

Even where evidence is not subject to a mandatory exclusionary rule, it may be excluded under discretionary provisions:

• Section 135: General discretion to exclude evidence where probative value is substantially outweighed by prejudice, confusion, or waste of time
• Section 137: Mandatory exclusion in criminal proceedings where probative value is outweighed by unfair prejudice
• Section 138: Discretionary exclusion of improperly or illegally obtained evidence

Weight: The Assessment Function

Once evidence is admitted, the tribunal of fact must assess what weight to give it. This assessment is unconstrained by legal rules — it is a matter of fact-finding judgment.

Factors Affecting Weight

The weight given to evidence depends on multiple factors:

• Reliability: How likely is the evidence to be accurate?
• Corroboration: Is the evidence supported by other evidence?
• Consistency: Is the evidence internally consistent and consistent with other established facts?
• Source credibility: How reliable is the witness or source of the evidence?
• Circumstances of creation: Under what circumstances was the evidence created or obtained?

No Minimum Weight

Critically, there is no minimum weight that must be given to admissible evidence. A tribunal of fact is entitled to give evidence no weight at all, even if it has been admitted. This is particularly important where evidence is admitted subject to objection — admission does not compel acceptance.

Evidence Continuum Application

The CORE Defence Evidence Continuum directly addresses the admissibility-weight distinction. Stages 1-5 (Collection, Preservation, Interpretation, Reliability, Admissibility) relate primarily to admissibility questions. Stage 6 (Weight) addresses the separate question of how much reliance the evidence deserves.

Practical Illustrations

Hearsay Evidence

A witness's statement about what someone else told them may be excluded under the hearsay rule. If admitted under an exception (such as section 65 for first-hand hearsay), the tribunal must still assess weight. The fact that evidence was admitted under a hearsay exception does not mean it deserves the same weight as direct evidence.

Identification Evidence

Identification evidence may satisfy admissibility requirements while deserving careful scrutiny on weight. Courts recognise that identification evidence is inherently problematic, and tribunals of fact should approach it with caution regardless of admissibility.

Tendency Evidence

Tendency evidence admitted under section 97 may be given varying weight depending on its strength, proximity in time, and the degree to which it supports the tendency asserted. Admission does not determine weight.

Expert Evidence

Expert opinion may be admitted under section 79 yet be given limited weight if the underlying methodology is questionable, the expert's assumptions are not established, or contrary expert opinion exists.

Strategic Implications

For the Prosecution

The prosecution must appreciate that securing admission of evidence is only the first step. Evidence must also be capable of bearing the weight the prosecution seeks to place on it. A case built on admissible but weak evidence may not satisfy the beyond reasonable doubt standard.

For the Defence

Defence strategy involves decisions about where to challenge evidence. Options include:

• Admissibility challenge: Seeking exclusion of the evidence entirely
• Weight challenge: Accepting admission but arguing the evidence deserves little or no weight
• Combined approach: Challenging admissibility and, if unsuccessful, attacking weight

The appropriate strategy depends on the nature of the evidence, the strength of admissibility arguments, and the overall case theory. Sometimes accepting admission while attacking weight is more effective than a failed admissibility challenge.

Voir Dire Procedure

Admissibility questions are typically determined on a voir dire — a trial within a trial conducted in the absence of the jury. The judge hears evidence and argument on the admissibility question and rules before the jury is exposed to the evidence.

This procedure protects the jury from being influenced by evidence that should not be admitted. However, it means that admissibility rulings are made without the benefit of seeing how the evidence fits within the overall trial context.