12.108 In DP 69 the Commissions proposed that there be an exception to the credibility rule to allow the admission of expert evidence. This proposal arose out of a concern that, in a number of situations where such evidence would be relevant to the fact-finding process, Part 3.7 operates to exclude its admission. While there is no specific provision which excludes expert opinion evidence relevant to credibility, the provisions of Part 3.7 operate indirectly to exclude such evidence either because it is sought to be led in chief, or because it cannot be led in rebuttal because it is not appropriate to cross-examine on the issue.
12.109 Questions of expert evidence relevant to the credibility of witnesses were also discussed in Chapter 8 of DP 69. There, the Commissions discussed the need to clarify the admissibility of expert opinion evidence on the behaviour and development of children and raised the possibility of further clarification in relation to other topics of expert opinion. However, as noted in DP 69 and Chapter 9 of this Report, in most instances it is the credibility provisions, and not the opinion provisions, that present a significant barrier to the admission of such evidence.
12.110 In Chapter 9 of this Report the Commissions recommend that there be an amendment to the uniform Evidence Acts to clarify that expert opinion evidence can be led on the behaviour and development of children. The Commissions do not recommend any further clarification in relation to other categories of expert evidence. In the Commissions’ view it is unnecessary to clarify that such evidence can be admitted.
12.111 The discussion below demonstrates that the recommended exception to the credibility rule should allow the admission of expert evidence in at least two further situations:
- expert opinion evidence in relation to any relevant cognitive impairment of the witness; and
- expert opinion evidence on the effects and experience of family violence where that is relevant to the credibility of a witness.
12.112 At common law there is well established authority for the proposition that expert evidence may be led as to a mental or physical impairment of a witness relevant to assessing his or her credibility. In Toohey v Metropolitan Police Commissioner, the House of Lords held that an accused person should be permitted to adduce medical evidence as to the hysterical and unstable nature of the alleged victim of an assault. Lord Pearce commented:
Human evidence shares the frailties of those who give it. It is subject to many cross-currents such as partiality, prejudice, self-interest and, above all, imagination and inaccuracy. Those are matters with which the jury, helped by cross-examination and common sense, must do their best. But when a witness through physical (in which I include mental) disease or abnormality is not capable of giving a true or reliable account to the jury, it must surely be allowable for medical science to reveal this vital hidden fact to them. If a witness purported to give evidence of something which he believed that he had seen at a distance of 50 yards, it must surely be possible to call the evidence of an oculist to the effect that the witness could not possibly see anything at a greater distance than 20 yards, or the evidence of a surgeon who had removed a cataract from which the witness was suffering at the material time and which would have prevented him from seeing what he thought he saw. So, too, must it be allowable to call medical evidence of mental illness which makes a witness incapable of giving reliable evidence, whether through the existence of delusions or otherwise.
12.113 The statement by Lord Pearce that it is ‘obviously in the interest of justice that such evidence should be available’ is one that is hard to dispute, although at times reservations have been expressed about admitting such evidence.
12.114 The admissibility of this evidence under the uniform Evidence Acts is less clear. A broad interpretation of s 106(d), which lifts the credibility rule for evidence that tends to prove that ‘a witness is, or was, unable to be aware of matters to which his or her evidence relates’, could allow the admission of evidence of ‘psychological, psychiatric or neurological considerations’. However, this is still a more limited proposition than the common law in Toohey.
12.115 By removing the limits to the categories of credibility evidence which can be led from other witnesses, the revised s 106 provides greater scope to admit the type of opinion evidence admitted at common law. However, the admission of evidence under s 106 is conditional upon the matters being put to the witness in cross-examination and denied (or not admitted). This requirement poses difficulties which could unfairly prevent the admission of important evidence.
12.116 For example, in evidentiary terms, the question of whether a witness has some form of cognitive impairment is a matter of opinion. A witness with cognitive impairment may be able to be questioned about the effects of the condition as they experience them. Objection can be taken, however, to the witness giving evidence that he or she has a certain condition and that the condition is the cause of certain effects, as the witness may not be appropriately qualified to give that evidence. The witness may or may not be able to give evidence that he or she has been told of his or her condition and its effects by a suitably qualified expert. The evidence should not be excluded merely because the cross-examiner is not able to obtain the necessary denial/non-admission from the witness.
12.117 There will also be cases where parties want to lead evidence from an expert relevant to the credibility of their own witness whom they cannot cross-examine. The situations discussed in Chapter 9 are instances of this type of situation, as is R v Rivkin.
12.118 Expert evidence on the behaviour and development of children, the long term effects of family violence and the effects of various forms of cognitive impairment may enable the tribunal of fact to better evaluate the credibility of witnesses. This evidence is particularly important to prevent misinterpretation of, and inappropriate inferences based on uninformed reasoning being drawn from, behaviour. The evidence may prevent adverse inferences being drawn as to credibility, or may cast doubt on the credit of the witness as demonstrated in the cases in which Toohey has been applied.
12.119 For example, in Coombe v Bessell the trial judge drew adverse inferences as to the credibility of the defendant from his manner of speech in giving evidence, and convicted him of assault. On a motion to review it was held that evidence of the defendant’s speech impediment was admissible because if it was not revealed, the court would be prevented from properly assessing the evidence.
12.120 In R v Edwards a new trial was ordered on the basis that evidence had become available that the main prosecution witness at trial suffered from severe immature histrionic personality disorder. In that case Wallace J commented that ‘to fail to have before the jury the psychiatric evidence involved would be to deprive it of all that it was entitled to know for the purpose of arriving at a just verdict’.
12.121 The Commissions came to the preliminary view in DP 69 that such cases need to be addressed by providing a further exception to the credibility rule to allow expert evidence to be called. The solution proposed was to provide that the credibility rule does not apply to expert opinion evidence capable of substantially affecting the assessment of the credibility of the witness, subject to the leave of the court.
12.122 A draft of a new s 108AA was included in DP 69. This includes a provision mirroring that under Proposal 9–1 to clarify that evidence can be led under the section in relation to the development and behaviour of children generally and the development and behaviour of victims of child sexual assault. This clarification is designed to overcome a demonstrated reluctance of courts to accept that the development and behaviour of children is a matter of specialised knowledge outside the general knowledge of the community.
Submissions and consultations
12.123 The Law Society of NSW opposes Proposal 11–6 on the basis that it would add to the time and costs of litigation, with little benefit.
12.124 The NSW DPP, the Intellectual Disability Rights Service, Justice Branson and Justice French support the proposal. The NSW PDO supports the proposed amendment with the exception of the specific reference to evidence of child development. It argues that preference should not be given to any particular kind of expert evidence and points to the importance of expert evidence in relation to the unreliability of eyewitness identification evidence.
12.125 Others express support for an exception to the credibility rule in relation to some expert evidence, but urge the Commission to consider a more limited provision. There is support for ensuring that the uniform Evidence Acts are amended to make admissible the type of evidence admitted in Toohey, but to limit any amendment to that situation.
12.126 The Criminal Law Review Division of the New South Wales Attorney General’s Department draws attention to the provisions which have been enacted in relation to expert opinion evidence concerning child victims of sexual assault in New Zealand, and the law on this issue in the United States. The New Zealand provision is a very specific one. It allows appropriately qualified child psychiatrists and psychologists to give evidence in child sexual abuse cases as to the intellectual attainment, mental capability and emotional maturity of the complainant, the general level of development of children of the same age group and whether any evidence relating to the complainant’s behaviour is consistent or inconsistent with the behaviour of sexually abused children of the same age group. The New Zealand Court of Appeal has interpreted the provision in such a way as to give it a very confined operation. The concern, both in New Zealand and the United States, has been that expert evidence that the behaviour of the complainant is consistent with that of a child victim of sexual abuse should not be used as evidence that the child was in fact abused. Proper directions should be given to juries to that effect.
12.127 A concern is also expressed in submissions and consultations that the introduction of the exception by allowing expert evidence to be called from both sides may lead to undesirable expert battles. In particular, while supporting the amendment of the uniform Evidence Acts to allow for the admission of expert opinion evidence on the credibility and reliability of victims of family violence, the Women’s Legal Service Victoria opposes any provision which will allow defendants to raise questions of credibility and reliability of evidence of victims of violence, merely on the basis of their being a victim of violence.
The Commissions’ view
12.128 The Commissions share the concerns expressed as to the potential to add to the time and cost of litigation of the proposed exception to the credibility rule. However, the Commissions maintain that it is clear that the uniform Evidence Acts should provide an exception for expert testimony to prevent injustice to the parties and ensure a proper factual basis for the evaluation of the credibility of witnesses. The issue is then how best to control admissibility and confine that evidence within appropriate limits.
12.129 Several limitations were imposed on the admission of the evidence under Proposal 11–6 in DP 69. The draft s 108AA provided that the evidence:
- must be wholly or substantially based on the specialised knowledge of the witness;
- must be capable of substantially affecting the credibility of the witness; and
- may only be adduced with the leave of the court (importing the considerations in s 192 including whether admission of the evidence will unduly add to the length of the trial, the importance of the evidence and fairness to the parties or a witness).
12.130 Further, s 137 requires the court to exclude evidence which is unfairly prejudicial to a defendant in criminal proceedings, and s 136 allows the court to limit the use the tribunal of fact may make of the evidence. For example, if evidence of the behaviour and development of victims of child sexual assault is admitted, the court may direct that the evidence only be used for the credibility purpose and not to reason that, because the behaviour of the complainant is consistent with that of a victim of child sexual abuse, the complainant was abused.
12.131 Creating an exception for expert evidence may mean that in some cases experts with opposing views may be called. The Commissions believe that it is an unavoidable consequence of the adversarial system that each side has the opportunity to call evidence to contradict that of the other, should such evidence be available. The Commissions maintain that it is preferable to allow the tribunal of fact to assess two opinions than remove such opinions from its consideration.
12.132 The Commissions also maintain that clarification of the admissibility of expert evidence relating to the behaviour and development of children is justified on the basis of the demonstrated reluctance of some judicial officers to accept that this is a relevant field of expertise and a matter beyond the ‘common knowledge’ of the tribunal of fact. The inclusion of the provision does not connote that undue prominence should be given to this evidence, and should not be seen as taking away from the generality of the provision.
12.133 In the Commissions’ view, the uniform Evidence Acts should be amended to include a new exception to the credibility rule relating to expert testimony of substantial probative value, subject to the leave of the court. The new provision should be drafted to attract the admissibility requirements of s 79 of the uniform Evidence Acts. A draft provision (s 108AA) is set out in Appendix 1.
Recommendation 12–7 The uniform Evidence Acts should be amended to include a new exception to the credibility rule which provides that, if a person has specialised knowledge based on the person’s training, study or experience, the credibility rule does not apply to evidence given by the person, being evidence of an opinion of that person that: (a) is wholly or substantially based on that knowledge; and (b) could substantially affect the assessment of the credibility of a witness; and (c) is adduced with the court’s leave. The Acts should also include a provision clarifying that the evidence to which the exception applies includes evidence about child development and behaviour (including the effect of sexual abuse).
 In which case it is excluded by s 102.
 See Australian Law Reform Commission, New South Wales Law Reform Commission and Victorian Law Reform Commission, Review of the Uniform Evidence Acts, ALRC DP 69, NSWLRC DP 47, VLRC DP (2005), [11.100]–[11.110].
 Including Evidence Act 2001 (Tas) s 79A
 See Rec 9–1.
Toohey v Metropolitan Police Commissioner  AC 595; Farrell v The Queen (1998) 194 CLR 286; R v Edwards (1986) 20 A Crim 3 463; R v Y (1995) 81 A Crim R 446.
Toohey v Metropolitan Police Commissioner  AC 595.
 Ibid, 608.
 Ibid, 608.
 For example, R v Turner  QB 834, 842; R v Smith  VR 907.
R v Souleyman (Unreported, New South Wales Supreme Court, Levine J, 5 September 1996). See also S Odgers, Uniform Evidence Law (6th ed, 2004), [1.3.8200].
 A term which includes mental illness, intellectual disability and personality disorders.
R v Rivkin (2004) 59 NSWLR 284.
Coombe v Bessell (1994) 4 Tas R 149.
R v Edwards (1986) 20 A Crim R 463.
 Ibid, 466–467.
 See Ch 9.
 The Criminal Law Committee and the Litigation Law and Practice Committee of the Law Society of New South Wales, Submission E 103, 22 September 2005.
 Director of Public Prosecutions (NSW), Submission E 87, 16 September 2005.
 Intellectual Disability Rights Service, Submission E 101, 23 September 2005.
 Justice C Branson, Consultation, Sydney, 25 July 2005.
 Justice R French, Submission E 119, 6 October 2005.
 New South Wales Public Defenders Office, Submission E 89, 19 September 2005.
 Confidential, Submission E 63, 29 August 2005; NSW Attorney General’s Department Criminal Law Review Division, Submission E 95, 21 September 2005.
 Confidential, Submission E 63, 29 August 2005.
 NSW Attorney General’s Department Criminal Law Review Division, Submission E 95, 21 September 2005.
Evidence Act 1908 (NZ) s 23G.
 Rosemount Youth and Family Services, Submission E 107, 15 September 2005; Women’s Legal Services Victoria, Submission E 110, 30 September 2005; Victorian Roundtable 30 August 2005.
 Women’s Legal Services Victoria, Submission E 110, 30 September 2005 in response to Australian Law Reform Commission, New South Wales Law Reform Commission and Victorian Law Reform Commission, Review of the Uniform Evidence Acts, ALRC DP 69, NSWLRC DP 47, VLRC DP (2005), Q 8–2.
 Providing a means to address the type of concerns which are addressed in a more explicit way by the New Zealand provisions raised in NSW Attorney General’s Department Criminal Law Review Division, Submission E 95, 21 September 2005.