Evidence is not proof — the adversarial approach to establishing truth — (2024) 32(8) ARM 103

Commercial Law
Haley Aprile

This article was first published in the May 2024 edition of the Australian Risk Management Journal. 

When one thinks about cases which are determined by the courts, it is probably safe to say that most people believe that the court is tasked with determining the truth. And that therefore, the evidence which is put before the court in order to assist it in that determination, must go towards establishing the truth. However, in an adversarial legal system, which Australia’s is, that is not necessarily the case. Rather, given that the proceeding is essentially a contest between the parties to the proceeding,1 the court is in fact tasked with determining which party’s version of the truth ought more readily be accepted than the other party’s version,2 to the requisite standard of proof.

Further, simply because a particular piece of evidence appears to be relevant to the case at hand, does not mean that it will be admitted into evidence and thereby considered by the decision maker (whether it be a judge or a jury). That is so because the rules of evidence which govern court proceedings may apply so as to exclude what appears to be obviously relevant evidence.

Although this may appear counterintuitive, the reason for this, arising from our adversarial system of justice, is to ensure that matters are conducted fairly as between the parties. The rules of evidence seek to combat the risk that the decision maker will make an incorrect assessment of the value of, or the weight to give to, a particular piece of evidence, or may otherwise be confused or misled. Because the decision maker, being either a judge or jury, will be occasioned by human frailties, and imbued with their own backgrounds and experiences (however much they might try not to be influenced by them),3 fairness is sought to be achieved by keeping evidence which might unfairly prejudice one of the parties out of the decision maker’s consideration.4 On the law of evidence, one commentator stated “founded apparently on the propositions that all jurymen are deaf to reason, that all witnesses are presumptively liars and that all documents are presumptively forgeries”.5

As well as ensuring an even playing field as between the parties, the rules of evidence also seek to reflect and protect our societal values, even if that means that sometimes the protection of those values is more important than ensuring all the evidence is before the court in a particular case.6 The rules concerning the privilege against self-incrimination and the exclusion of illegally or improperly obtained evidence are good examples of this.

As important as these rules of evidence appear to be, they are not mandated in all settings in which there is a legal contest or dispute between parties. For example, royal commissions and inquiries are not bound by the rules of evidence, and neither are many tribunals. Notwithstanding that they are not bound by them, and although they might not strictly adhere to them, these non-courts often do employ the rules of evidence in some way. Accordingly, their importance to our system of justice cannot be overlooked.

Below is a discussion of some of the more important and most common rules of evidence which may serve to limit or exclude from the consideration of the decision maker, what might otherwise be relevant evidence in a particular case. Many, if not all, of these rules have their foundations in the common law (colloquially known as “judge-made” law), but have been codified in the Uniform Evidence Law. For ease, references to the Uniform Evidence Law throughout this article are to the Commonwealth Evidence Act 1995 (NSW).

Relevance — the fundamental rule of evidence

Subject to any exceptions, evidence that is relevant to a fact in issue in a proceeding is admissible in the proceeding.7 It may then appear to be a simple exercise of determining whether a piece of evidence is relevant or not to a particular dispute. However, the determination is not as simple as it may appear at first blush. The test of whether evidence is “relevant” is whether, if it were accepted, the evidence could rationally affect (directly or indirectly), the assessment of the probability of the existence of a fact in issue in the proceeding.8 Put simply, there must be, objectively, a rational connection between the evidence and the fact in issue.9 Making this determination is, in my opinion, not always a simple task. However, the following quote provides a useful illustration on how the determination may be approached:

… [evidence may be ] … so inherently incredible, fanciful or preposterous that it could not be accepted by a rational jury. In such a case its effect on the probability of the existence of a fact in issue would be nil and it would not meet the criterion of relevance.10

The rule against hearsay evidence

Another well-known rule of evidence is the rule against hearsay. Where a statement made to a witness by another person who is not themselves called as a witness, is sought to be adduced as evidence, and the purpose of adducing the evidence is to establish the truth of what is contained in the statement, the rule against hearsay renders the statement inadmissible.11 That is not to say that the statement may not be admitted into evidence for some other purpose, so long as that other purpose is not to establish the truth of the statement. For example, evidence of a previous statement may be adduced not to prove the truth of the statement, but that the maker can speak English.

It is said that the rule was developed because it was thought that a jury did not have the capacity to evaluate hearsay evidence, that is, jurors may give hearsay evidence more weight they than should when compared with direct evidence12 and/or because of the unfairness in not allowing a party to cross-examine the maker of the statement.13

Logically, it makes sense that if decision-makers are being asked to accept as true, a prior statement which was made, then they ought to hear that statement “from the horse’s mouth” and have the ability to cross-examine the maker of the statement to test its veracity. Further, it is well accepted that there is an inherent “danger of inaccuracy through repetition”,14 as demonstrated by a game of “Chinese whispers”.

There are also a number of exceptions to the rule which would permit the evidence to be adduced for the purposes of proving the truth of the statement, including so-called “dying declarations”, statements in public documents and business records, and confessions or admissions, amongst others. For example, the rule against hearsay does not apply to evidence of an admission, so long as the witness giving the evidence saw, heard or perceived the admission being made.15

The rule against opinion evidence

This rule prevents the admission of an opinion to prove the existence of a fact about the existence of which the opinion was expressed.16 Here, an “opinion” means “any inference from observed or assumed facts”.17 In short, the rule prevents witnesses from giving an opinion on matters requiring specialist knowledge or skill. The rationale for the rule is that a witness should only provide evidence about facts which they directly observed or perceived and it is for the judge or jury to draw inferences from that evidence.18

However, there are two exceptions to the rule:

  • where specialised skills or knowledge is required in order to be able to draw inferences from the evidence, an expert witness with the specialised skills and knowledge required, is permitted to give that evidence19 and
  • where a non-expert opinion is based on what a witness directly saw, heard or perceived about a matter or event20

The rule against tendency evidence

Also known as “similar fact evidence”, this rule applies mainly to criminal proceedings. It prevents the prosecution from adducing evidence of the character, reputation, conduct or tendency that a person has or had, in order to prove that they have or had, a tendency to act in a particular way or a particular state of mind. The exception to the rule being that the evidence is of such high probative value so as to substantially outweigh any prejudice it may cause.21


Along with the exclusionary rules of evidence, there are also a number of privileges which, if claimed by a party, will often result in relevant evidence being excluded.

Those privileges include legal professional privilege, which encompasses client-legal privilege22 and litigation privilege.23 These privileges result in a party not being permitted to adduce evidence, if on objection by the other party, it would result in the disclosure of a confidential communication which was made either for the purposes of obtaining or giving legal advice or for use in actual or contemplated legal proceedings.

There are also privileges relating to the non-disclosure by journalists of evidence regarding an informant’s identity24 and the non-disclosure of a religious confession, unless the confession was made for a criminal purpose.25

However, the most commonly known privilege is the privilege against self-incrimination,26 whereby a witness can object to giving evidence on a particular matter because they consider that doing so may tend to prove either that they have committed an offence (in Australia or another jurisdiction), or render them liable to a civil penalty. If the court determines that there are reasonable grounds for the objection, then the witness will usually not be required to give the evidence. It is possible for the court to find that there are reasonable grounds for the objection and still require that the evidence be given, because the court is satisfied that it is in the interests of justice to do so and the evidence does not tend to prove that the witness has committed an offence or would be liable to a civil penalty.27

Other exclusionary rules

There are also a number of general rules which either mandate that the court exclude or limit the use of particular evidence, or which give the court a discretion to determine whether to exclude or limit evidence.

In both civil and criminal proceedings, the court has a discretion to refuse to admit evidence if it considers that the probative value of the evidence is substantially outweighed by the danger that the evidence might be unfairly prejudicial to a party, or may otherwise be misleading or confusing, amongst other things.28 Evidence is considered to be unfairly prejudicial where there is a danger that the jury will misuse the evidence — either by misjudging the weight to be given to the evidence; where there is an inability to test the evidence; or where the evidence will be incomplete.

In the context of a criminal proceeding, the court is mandated to refuse to admit evidence sought to be adduced by the prosecution if its probative value is outweighed by the danger of unfair prejudice to the accused.29

Likewise, in relation to evidence that was obtained by, or as a consequence of, improper means or in contravention of Australian law, a court must not admit such evidence unless the desirability of admitting it outweighs the undesirability of admitting it due to the way in which it was obtained.30


The brief review of some of the rules of evidence above illustrates that although the rules are somewhat complicated, they ensure not only fairness between the parties to litigation, but seek to uphold societal values, even if that means that sometimes not all of the relevant evidence is before the court.

1 As opposed to an inquisitorial system in which the court is actively involved in investigating the matter before it, including by the examination of witnesses.

2 The Hon S Gageler AC “Evidence and Truth” (2017) 13 (3) The Judicial Review 249, 252.

3 Above, 255–56.

4 Above n 2, at 252.

5 C P Harvey “The Advocate’s Devil” (1959) 72(4) Harvard Law Review 794.

6 Above n 2, at 251.

7 Evidence Act 1995 (Cth), s 56.

8 Above, at s 55(1).

9 Harrington-Smith obh of The Wongatha People v Western Australia (No 7) (2003) 130 FCR 424; [2003] FCA 893; BC200305096 at [11] per Lindgren J.

10 IMM v R (2016) 257 CLR 300; 330 ALR 382; [2016] HCA 14; BC201602516 at [39] per French CJ, Kiefel, Bell and Keane JJ.

11 Above n 7, s 59.

12 The Hon J D Heydon “Cross on Evidence Cross” LexisNexis Australia (online at 15 February 2024), at [31020].

13 Above, at [31015].

14 Above n 12, at [31020].

15 Above n 7, s 81(1).

16 Above n 7, s 76.

17 Above.

18 Above n 12, at [29005].

19 Above n 7, s 79; above n 12, at [29005].

20 Above n 7, s 78.

21 Above n 7, s 97.

22 Above n 7, s 118.

23 Above n 7, s 119.

24 Above n 7, s 126K(1).

25 Above n 7, s 127 EA.

26 Above n 7, s 128 EA.

27 If the court requires a witness to give evidence, despite the witness’ objection, or the witness voluntarily gives the evidence without being required to do so, the court must give the witness a certificate of immunity under s 128(5) of the Evidence Act. Such a certificate means that the evidence given cannot be used against the witness in another proceeding pursuant to s 128(7) of the Evidence Act.

28 Above n 7, s 135.

29 Above n 7, s 137.

30 Above n 7, s 138.

Haley Aprile

Haley Aprile has significant expertise in regulatory, commercial and public law.

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