9.123 Section 80 of the uniform Evidence Acts also abolished the common knowledge rule—the rule that excluded expert opinion evidence in areas said to be areas of common knowledge. Section 80(b) provides:
Evidence of an opinion is not inadmissible only because it is about:
(b) a matter of common knowledge.
9.124 The ALRC was critical of the common knowledge rule. It identified significant uncertainty in the common law, where one of two views is taken. One view is that the mere existence of an area of common knowledge precludes reception of expert evidence in the area. The second approach is to ask whether the tribunal of fact is ‘competent’ to reach an informed decision without the advantage of the opinion: where it is, the opinion evidence is inadmissible. The ALRC commented that a clear definition of what is ‘common knowledge’ is impossible. It also expressed the view that the exclusion lacked theoretical justification because there are many situations in which the trier of fact might have some acquaintance with a subject, along with the rest of the community, but might nevertheless find expert assistance on the subject valuable.
9.125 The ALRC referred to the fact that one of the consequences of the common knowledge rule has been to deny courts testimony on the working of memory, on the process of identification, and generally on the mental function of persons not suffering recognised psychiatric disease. Much valuable research is done in areas that would be classified by the courts as falling within ‘common knowledge’, on this approach. To refuse to receive such evidence has the result that decisions can be based on knowledge that is incomplete and out-of-date. The ALRC recommended that, rather than ask whether the area in relation to which expert opinion evidence is tendered is one of common knowledge, the question for the court should be whether the trier of fact could usefully receive assistance from the expert opinion evidence. The view was taken that s 135 of the uniform Evidence Acts provides the appropriate controls. To that may be added the relevance requirement under s 55.
9.126 Suggestions were noted in IP 28 that, as a result of the abolition of the common knowledge rule, dealing with evidence about such matters as motor vehicle accident reconstruction, which may have been excluded by the application of the common law rules, involves unnecessary time and expense.
9.127 The Commissions note that, in particular, s 80 may have facilitated attempts to introduce expert opinion evidence in relation to identification. Such evidence involves opinion based on knowledge of research by psychologists into factors affecting the accuracy of eyewitness identification. The Commissions also understand that expert evidence on ‘facial mapping’ using data from facial recognition information technology is increasingly being used in criminal proceedings. Under the common law, such expert opinion evidence in relation to identification is generally inadmissible because it concerns a matter ‘within the range of human experience which must be determined by the jury’.
9.128 In R v Smith, it was accepted that because the uniform Evidence Acts expressly abolish the common knowledge rule, identification expert evidence may fall within s 79 of the Act. Smart AJ noted that ‘the routine admission of expert evidence in cases where identification was the main issue would lengthen the hearing of these cases and to some extent change the way in which they are conducted’. The New South Wales Court of Criminal Appeal held that the particular expert identification evidence, if tendered as fresh evidence at trial, should be excluded under s 135(c) of the New South Wales Act as likely to cause or result in undue waste of time.
9.129 Earlier in the Inquiry, it was asked whether concerns exist with regard to the admission of expert opinion evidence on matters of common knowledge; for example, in relation to expert identification evidence or motor vehicle accident reconstruction. Subsequently, in DP 69, the Commissions said they considered that there is no reason to reintroduce the common knowledge rule.
Submissions and consultations
9.130 In response to DP 69, the Law Institute of Victoria submits that the common knowledge rule should not be abolished if Victoria adopts the uniform Evidence Act because of what is said to be the ‘high risk that juries might rely on, or afford particular probative value to, expert evidence on matters of common knowledge’. Section 135 is said to ‘provide insufficient exclusionary power’ to protect against the perceived risk.
9.131 Professor Kathy Mack submits that ‘common knowledge’ is problematic throughout evidence law and practice because experience ‘is not necessarily common, and knowledge thought to be general might be specific to particular individuals or groups’.
This is especially problematical when the experience which controls [the admissibility of evidence] is that of the judge, and it differs significantly from the experiences of other groups in society especially litigants or parties before the court.
9.132 While acknowledging that ‘such beliefs are implicated in all inferential reasoning about facts’, Professor Mack submits that any reliance on common experience ‘should at the very least be articulated and expressed so that [the beliefs] can be tested’.
9.133 In consultations held by the Victorian Law Reform Commission, a Supreme Court judge said that great difficulties arise where an expert strays outside his or her area of expertise because a jury might give undue weight to the opinion. The common knowledge rule is said to prevent these difficulties. Another participant supported that position.
The Commissions’ view
9.134 The effect of s 80(b) of the uniform Evidence Acts is that evidence previously of doubtful admissibility because of the common knowledge rule, for example evidence from psychologists or psychiatrists about human behaviour or on child development, is admissible, subject to ss 135–137. Section 80(b) also removes the difficulty that, where an expert gives opinion evidence relying partly on specialised knowledge based on the expert’s training, study or experience, and relying partly on matters of common knowledge, the opinion would strictly be inadmissible if common knowledge formed a substantial part of the basis of the opinion. In that respect, it complements and is complemented by s 79, which makes admissible expert opinion evidence complying with the elements of the section ‘that is wholly or substantially based on’ expert knowledge.
9.135 The following can be said regarding experts straying outside their fields of expertise. That the problem has arisen in jurisdictions such as Victoria where the common knowledge rule applies shows that the mere existence of the rule is not itself preventive of the problem. Under the uniform Evidence Acts, s 79 confines the scope of admissible expert opinion evidence to evidence that is ‘wholly or substantially’ based on the person’s expert knowledge. Opinion not at least substantially based on expert knowledge is not within the s 79 exception. Even before reaching that stage, s 55 might render the opinion inadmissible if it is based too heavily on matters of common knowledge, because the opinion could be incapable of rationally affecting the assessment of the probability of the existence of a fact in issue.
9.136 The Commissions consider that s 135, as presently drafted, provides adequate grounds on which to exclude evidence on matters of common knowledge. Any adverse consequences of the enactment of s 80(b) can be addressed by a robust application of s 135(c). Limiting orders can also be made under s 136. In criminal cases, s 137 in some cases requires the court to exclude opinion evidence based on common knowledge, further filtering the evidence. Such an approach provides adequate latitude for courts to exclude evidence on matters of common knowledge.
9.137 The Commissions do not consider that there is any reason to propose the reintroduction of the common knowledge rule. However, this is another area that should be considered in any program of continuing education on the operation of the uniform Evidence Acts. The Commissions refer to the discussion in Chapter 3.
 Ibid, .
 Ibid, .
 Australian Law Reform Commission, Review of the Evidence Act 1995, IP 28 (2004), [6.52].
 This may address historic problems with the handling of eyewitness identification, by allowing juries and judicial officers to be informed by the psychological evidence about the unreliability of eyewitness accounts.
 New South Wales Local Court Magistrates, Consultation, Sydney, 5 April 2005.
Smith v The Queen (1990) 64 ALJR 588, 588.
R v Smith (2000) 116 A Crim R 1.
 Ibid, .
 Ibid, .
 Australian Law Reform Commission, Review of the Evidence Act 1995, IP 28 (2004), Q 6–7.
 Law Institute of Victoria, Submission E 116, 27 September 2005.
 K Mack, Submission E 82, 16 September 2005.
 Victorian Law Reform Commission Roundtable, Consultation, Melbourne, 18 August 2005.