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Published online by Cambridge University Press: 01 January 2025
The ‘basis rule’ is, in general terms, a rule which restricts expert witnesses to giving opinion evidence in respect of which there is or will be proof, by other admissible evidence, of the facts and assumptions upon which the opinion is based. There has been no clear consensus as to whether the basis rule exists either at common law or under the Uniform Evidence Legislation, or whether the rule goes to admissibility or weight. This article examines the jurisprudence, with a particular focus on the recent High Court decision of Dasreef Pty Ltd v Hawchar. The authors argue that the controversy surrounding the basis rule has been the result of a misunderstanding and misconstruction of the rule. They argue that the conflict may be resolved by understanding the basis rule as simply a rearticulation, in the specific context of expert evidence, of the requirement that evidence must be relevant to be admissible. The weight of that expert evidence remains to be determined in accordance with ordinary principles.
The views expressed in this article are those of the authors and do not necessarily represent the views of Lipman Karas.
1 See generally Kumar, Miiko, ‘Admissibility of Expert Evidence: Proving the Basis for an Expert's Opinion’ (2011) 33 Sydney Law Review 427Google Scholar; Heydon, J D, Cross on Evidence (LexisNexis Butterworths, 9th ed, 2013) 967–73 [29070]Google Scholar; Freckelton, Ian and Selby, Hugh, Expert Evidence: Law, Practice, Procedure and Advocacy (Lawbook Co, 4th ed, 2009)Google Scholar ch 6 ‘The Basis Rule’; French, Robert, ‘Expert testimony, opinion, argument and the rules of evidence’ (2008) 36 Australian Business Law Review 263, 274–5Google Scholar; Hodgekiss, Christopher C, ‘Expert evidence in competition litigation’ (2006) 14 Trade Practices Law Journal 6, 11–13.Google Scholar
2 (2011) 243 CLR 588 (‘Dasreef’).
3 See ibid 612 [61].
4 Uniform evidence legislation has been enacted across a number of Australia jurisdictions following an inquiry by the Australian Law Reform Commission into the law of evidence which culminated in the publication of two reports: Evidence (Interim), Report No 26 (1985) (‘ALRC 26’); and Evidence, Report No 38 (1987). The adoption of the Commission's recommendations began with the enactment of the Evidence Act 1995 (Cth). New South Wales, Tasmania, Victoria and the Australian Capital Territory have since followed suit.
5 Some distinction has been drawn between facts which are ‘observed’ by the expert and facts which are ‘assumed’ or ‘accepted’ by the expert: see, eg, Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705, 743–4 [85]. As far as the basis rule is concerned, there is no practical difference between the two categories. Both kinds of facts find probity in other evidence. The difference is only in the source of that evidence: assumptions rely on proof by evidence not provided by the expert, while facts observed rely on proof by evidence to be provided by the expert him or herself. In this article, the term ‘factual basis’ of an opinion is employed to cover both facts observed and assumptions.
6 R v Bonython (1984) 38 SASR 45, 46 (King CJ).
7 See Dasreef (2011) 243 CLR 588, 635 [118] and discussion in Part IV-D. See also Freckelton and Selby, above n 1, 111.
8 See Kumar, above n 1, 432–3; Freckelton and Selby, above n 1, 113–14; ALRC 26, above n 4, vol 1 [161]; Australian Law Reform Commission, Uniform Evidence Law, Report No 102 (2005) 293–4 [9.57]–[9.58] ('ALRC 102’).
9 (2001) 52 NSWLR 705 (‘Makita’).
10 Clark v Ryan (1960) 103 CLR 486, 491.
11 See generally Idoport Pty Ltd v National Australia Bank Ltd [1999] NSWSC 828 (19 August 1999) [239]; Heydon, Cross on Evidence, above n 1, 953–4 [29045].
12 Section 56.
13 The status of these rules at common law is less clear. The common knowledge rule is more strictly adhered to than the ultimate issue rule but neither is categorically strictly applied to exclude opinion evidence which is considered to have probity for the court.
14 (Unreported, Supreme Court of New South Wales, McLelland J, 9 September 1987) 5.
15 The authorities which we examine in this Part have been commonly cited in numerous judgments of courts, including that of Heydon J in Dasreef, and writings of commentators, including those cited at Fn 1 and elsewhere in this article.
16 [1975] QB 834.
17 Freckelton and Selby, above n 1, 114. For example, R v Turner is cited with approval by Heydon J in Makita (2001) 52 NSWLR 705, 733 [69] and Dasreef (2011) 243 CLR 588, 614 [66].
18 [1975] QB 834, 840.
19 ALRC 26, above n 4, vol 2 [108].
20 Dasreef (2011) 243 CLR 588, 616 [74].
21 Freckelton and Selby, above n 1.
22 See [1975] QB 834, 841–2.
23 (1961) 108 CLR 642, 649.
24 See, eg, Palmer-Bruyn and Parker Pty Ltd v Parsons (2001) 208 CLR 388 [138] and the cases discussed below.
25 Dasreef (2011) 243 CLR 588, 620 [83]. The ALRC took the same view in ALRC 26, above n 4, Vol 2 [108].
26 Dasreef (2011) 243 CLR 588, 619 [80].
27 (1985) 62 ALR 85, 87–8 [9] (‘Paric’).
28 See, eg, Makita 731–2 [64] and Dasreef 613 [66].
29 Paric (1985) 62 ALR 85, 87–8 [9].
30 Paric v John Holland Constructions Pty Ltd (1984) 2 NSWLR 505, 510.
31 (1990) 24 FCR 313, 350–1.
32 Arnotts Ltd v Trade Practices Commission (1990) 24 FCR 313, 351.
33 (1995) 12 WAR 370, 387. This statement was repeated by Anderson J in Pollock v Wellington (1996) 15 WAR 1.
34 Pownall v Conlan Management Pty Ltd (1995) 12 WAR 370, 390.
35 Ibid.
36 Ibid.
37 Ibid 377 (emphasis added).
38 Ibid 377.
39 This is consistent with the way in which the High Court in Ramsay v Watson (1961) 108 CLR 642 dealt with the physician's opinion which was partly based on inadmissible hearsay. See also Heydon, Cross on Evidence, above n 1, 973 [29070].
40 ALRC 26, above n 4, vol 1 [750].
41 Ibid vol 1 [750].
42 Ibid vol 2 [108].
43 Ibid vol 1 [750].
44 The criticisms made by the Federal Court and Heydon J of the ALRC's view are discussed below at Parts III-C and IV respectively.
45 (2001) 52 NSWLR 705.
46 Makita (2001) 52 NSWLR 705, 731–2 [64] (references omitted).
47 (1999) 197 CLR 414 [39] (emphasis added), cited in Makita (2001) 52 NSWLR 705, 742 [84].
48 (2001) 52 NSWLR 705, 744 [85].
49 Ibid 745 [86].
50 [2002] NSWCA 165 (21 June 2002) [86] (emphasis added).
51 (2005) 218 ALR 764, 794 [136].
52 Ibid.
53 See, eg, Kumar, above n 1, 434 and cases cited therein.
54 French, above n 1, 274.
55 The respondent in Dasreef relied upon the three Federal Court cases which follow in support of the submission that there is no basis rule under the UEL.
56 (1998) 87 FCR 371, 373–4.
57 Ibid 374.
58 [2002] FCAFC 157 (4 June 2002) [7]–[8].
59 Ibid [14] (references omitted).
60 Ibid [87].
61 (2003) 134 FCR 208, 218 [22].
62 Ibid [24].
63 See (1999) 197 CLR 414 [39], cited in Makita (2001) 52 NSWLR 705, 742 [84].
64 Neowarra v Western Australian (No 1) (2003) 134 FCR 208, 218 [25].
65 ALRC 102, above n 8.
66 Ibid 292 [9.52].
67 Ibid 293 [9.54].
68 Ibid 292 [9.52] (emphasis added).
69 Ibid 293 [9.54].
70 Ibid.
71 Ibid 293–4 [9.57].
72 Ibid 295–6 [9.63].
73 Ibid 294 [9.58]. The ALRC cited Harrington-Smith v Western Australia (No 2) (2003) 130 FCR 424, 428 [22] where Lindgren J said (emphasis in original): ‘Discussions in the cases about these matters do not always clearly distinguish between that which a statement of expert opinion must contain in order to be admissible, and that which it should contain in order to be useful.’
74 ALRC 102, above n 8, 298 [9.70].
75 Ibid (emphasis in original).
76 Dasreef (2011) 243 CLR 588, 595 [6].
77 Ibid 594 [2].
78 Ibid 597 [15].
79 Ibid 598 [16].
80 Ibid 600 [22].
81 Ibid 602–3 [32].
82 Ibid 604 [39].
83 Ibid 605 [42].
84 Ibid 608 [49].
85 Walton Construction v Illawarra Hotel [2011] NSWSC 952 (23 August 2011) [11].
86 Dasreef (2011) 243 CLR 588, 605 [41].
87 Ibid.
88 Ibid.
89 Ibid 602 [31].
90 Ibid 613 [66].
91 Ibid.
92 Point (v) is consistent with the approach of Spigelman CJ in Australian Securities and Investments Commission v Rich (2005) 218 ALR 764, 794 [136], discussed above, that it is the asserted factual basis rather than true factual basis of an opinion which must be identified by the expert. See also Heydon, Cross on Evidence, above n 1, 954 [29045]; Odgers, Stephen, Uniform Evidence Law (Lawbook Co, 9th ed, 2010) 345 [1.3.4320].Google Scholar
93 Dasreef (2011) 243 CLR 588, 615 [68].
94 [2002] NSWCA 165 (21 June 2002) [86]. See also Heydon, Cross on Evidence, above n 1, 955 [29045].
95 ALRC 26, above n 4, vol 2 [108].
96 Dasreef (2011) 243 CLR 588, 620 [83].
97 Ibid 622 [89].
98 Ibid 620 [83].
99 Ibid, citing Ramsay v Watson (1961) 108 CLR 642, 649.
100 (1985) 62 ALR 85, 87–8 [9]. See Part III-A above for a discussion of this case, and the Court of Appeal decision from which case was appealed.
101 Cooper v Regina [2011] NSWCCA 258 (5 December 2011) [194].
102 See Coregas Pty Ltd v Penford Australia Pty Ltd [2012] NSWCA 350 (1 November 2012) [98]–[101].
103 Dasreef (2011) 243 CLR 588, 621 [86], citing Ramsay v Watson (1961) 108 CLR 642, 649.
104 Dasreef (2011) 243 CLR 588, 622 [90].
105 Ibid 622 [88]. See also Matthews v SPI Electricity Pty Ltd (Ruling No 24) [2013] VSC 269 (22 May 2013) [7]–[14], where J Forrest J said that ‘[t]here must be a point at which the divergence between the assumed facts and the established facts is so great that the opinion becomes irrelevant: that is, it does not satisfy the relevance test laid down by s 56 of the Act and is therefore inadmissible’.
106 Dasreef (2011) 243 CLR 588, 622 [89]. Heydon J quoted Eric v Preston Pty Ltd v Euroz Securities (2011) 274 ALR 705, 724 [171], where the Full Federal Court said: ‘The proposition that an expert's opinion based upon certain assumptions which are not ultimately proved in evidence is irrelevant is a fundamental principle of law’.
107 Ibid 620–1 [84].
108 Ibid 620 [83].
109 Ibid 605 [41].
110 Ibid.
111 Ibid 630–1 [106]–[107].
112 In Lithgow City Council v Jackson (2011) 244 CLR 352, 370 [43] French CJ, Heydon and Bell JJ (with whom Gummow and Crennan JJ agreed) cited Heydon J's approach in Dasreef as being the correct approach to applying ALRC material.
113 Dasreef (2011) 243 CLR 588, 631–2 [110].
114 Ibid 631 [109].
115 See ibid 631 [108].
116 Ibid 631 [109].
117 Ibid 631 [108].
118 Ibid 639 [133].
119 (2001) 206 CLR 650.
120 Ibid 653 [6] (Gleeson CJ, Gaudron, Gummow, Hayne JJ).
121 Ibid 655 [10].
122 Ibid 655 [11] (emphasis added). See also Odgers, above n 92, 344 [1.3.4320].
123 Dasreef (2011) 243 CLR 588, 605 [41].
124 Ibid.
125 Ibid 636 [120].
126 Smith v The Queen (2001) 206 CLR 650, 653 [6].
127 ALRC 26, above n 4, vol I, [363].
128 [2002] FCAFC 157 (4 June 2002) [16].
129 (2011) 243 CLR 588, 635 [118] (emphasis in original).
130 Ibid 635–6 [120].
131 See ibid 636 [123].
132 Ibid 615 [65].
133 See ibid 631 [108]. Section 57(1)(b) of the UEL states: ‘If the determination of the question whether evidence adduced by a party is relevant depends on the court making another finding (including a finding that the evidence is what the party claims it to be), the court may find that the evidence is relevant subject to further evidence being admitted at a later stage of the proceeding that will make it reasonably open to make that finding.’ This approach is consistent with that taken by J Forrest J in Matthews v SPI Electricity Pty Ltd (Ruling No 24) [2013] VSC 269 (22 May 2013) [14], where His Honour — unable to determine, at the moment of tender, the extent of divergence, if any, between assumed facts and the facts which will be ultimately established — considered it appropriate to admit the evidence provisionally under s 57 and allow the parties in closing submissions to further debate the question of admissibility of and weight to be given to the opinion.
134 For example, the other evidence goes only part of the way to establishing the factual basis of the opinion, in that the other evidence is capable of proving only some, but not all, factual assumptions.
135 See Traderight (NSW) Pty Ltd v Bank of Queensland Ltd (No 13) [2013] NSWSC 90 (19 February 2013) [12] where Ball J said: ‘It appears to follow from s 57(1) of the Act that opinion evidence is not admissible unless the court is satisfied that it is reasonably open to make the findings of fact on which the opinion is based either on the basis of evidence that has been admitted or on the basis of evidence that may be admitted at a later stage’.
136 For example, the other evidence is not capable of proving all the factual assumptions identified by the expert, but is nonetheless capable of proving the factual assumptions that are sufficient to form the basis of the opinion.
137 See Cadbury Schweppes Pty Ltd v Darrell Lea Chocolate Shops Pty Ltd (2007) 159 FCR 397, 420 [108] where Lindgren J said: ‘If the opinion is based on irrelevant facts or facts that are clearly not going to be proved, the opinion is likely to be valueless.’
138 In Traderight (NSW) Pty Ltd v Bank of Queensland Ltd (No 13) [2013] NSWSC 90 (19 February 2013) [15], Ball J said that ‘the extent to which opinion evidence satisfies the requirements set out by Heydon JA in Makita will be relevant to the exercise of the court's discretion under s 135 of the Act’. Thus, any failure to prove the factual basis of an opinion, which is not sufficiently grave to render the evidence irrelevant and inadmissible per se, may nevertheless give rise to circumstances that justify the exclusion of the opinion in exercise of the court's discretion or power under ss 135 or 137 of the UEL.
139 See, eg, Gilham v The Queen [2012] NSWCCA 131 (25 June 2012) [346].
140 See (2011) 243 CLR 588, 612–13 [64] (assumption identification rule), 622–4 [91]–[92] (statement of reasoning rule).
141 See ibid, 626–7 [100] (assumption identification rule), 638 [129] (statement of reasoning rule).
142 The statement of reasoning rule does not require that the court be satisfied that the stated reasoning is correct. The cogency of the expert's reasoning goes to weight only. See ibid 622–3 [91]–[92], 638 [129].
143 See ibid 628 [101] (assumption identification rule), 638–9 [130] (statement of reasoning rule).
144 Ibid 604 [37], quoting Makita (2001) 52 NSWLR 705, 744 [85].
145 HG v The Queen (1999) 197 CLR 414, 427 [39] (Gleeson CJ), quoted in Dasreef (2011) 243 CLR 588, 604 [36].
146 See, eg, Aytugrul v The Queen [2012] HCA 15 (18 April 2012) [32]; Illawarra Hotel Company Pty Ltd v Walton Construction Pty Ltd [2013] NSWCA 6 (11 February 2013) [101].
147 The source of this is the basic principle that expert opinion evidence must be of assistance to the court in order to be relevant and admissible: see R v Bonython (1984) 38 SASR 45, 46 (King CJ).
148 See Dasreef (2011) 243 CLR 588, 639 [133]; Harrington-Smith v Western Australia (No 2) (2003) 130 FCR 424, 428–9 [25]. On the relevance point, see also Odgers, above n 92, 344 [1.3.4320].
149 (2001) 52 NSWLR 705, 744–5 [86].
150 [2012] FCA 252 (19 March 2012) [411]–[412].
151 See Land Enviro Corp Pty Ltd v HTT Huntley Heritage Pty Ltd [2012] NSWSC 177 (5 March 2012) [42]–[43].
152 [2012] VSC 99 (30 March 2012) [86]–[98].
153 Ibid [97].
154 Ibid [98]. Dixon J here provided a useful summary reproducing the ‘rules’ applicable to evidence tendered under s 79 as stated by Heydon J.
155 [2011] NSWSC 963 (26 August 2011) [76].
156 [2013] NSWSC 1057 (14 August 2013) [130].
157 [2013] NSWCCA 114 (20 May 2013).
158 Ibid [61]–[68].
159 Ibid [164].
160 Ibid [176].
161 Ibid [177].
162 Ibid.
163 Ibid [179].
164 Ibid [139].