(1) The explanation for delay
18Having referred to KSE's evidence as to delay (at [32], [33]), the primary judge found that KSE was aware by late 2006 that there was a causation issue in relation to its existing claims. He also found that no application had been made to add a claim under s 1325(2) prior to 2011 because, until Mr Ashhurst SC had been retained in February 2011 and given advice in April 2011, "no one [had] thought of it": [34], [35]. His Honour was not prepared to conclude that KSE had deliberately held back in making its application to amend for any tactical reason: [35].
19When addressing the exercise of discretion in relation to the claims sought to be brought under s 1325(2), the primary judge noted:
"[116] ... From May 2011 until present those responsible for the conduct of the proceedings have pursued the application to amend with reasonable diligence although the first attempt to amend failed because the amendments were bad in form. ... Those circumstances still warrant a description of the delay as "gross" especially having regard to the inaction during the period prior to the retention of Mr Ashhurst SC, which included the date the limitation period expired. The material explaining the delay does not justify it."
20After referring to three specific matters concerning the effect of the delay, the primary judge continued:
"[125] A consideration of whether to exercise the discretion to grant the amendments necessary to mount a claim under s 1325(2) is more finely balanced than the consideration of whether to allow the amendments pleading a cause of action under s 1005 for an alleged breach of s 999. In light of conclusion I have reached at [109] the claim cannot be characterised as being of doubtful strength. In light of the explanation given to Harrison AsJ as to its rationale I accept that the proposed cause of action under s 1325(2) is likely to be "important" to KSE (Aon at [102]) or "critical" as asserted in its written submissions. However I am still left with an application that is made far too late with no proper explanation for the delay. The proposed amendments raise new factual issues. If granted they will require further particularisation and clarification which will cause additional delay and may expose more factual issues not previously raised by the pleading. The matter is now close to the allocated hearing date. If the application is granted, it is likely to lead to its vacation. To allow the amendments is otherwise capable of causing prejudice to the Pham defendants. To paraphrase Aon at [102] this is a case where it can "properly be concluded that [KSE] has had sufficient opportunity to plead [its] case and that it is too late for a further amendment, having regard to [the interests of the Pham defendants] and other litigants awaiting trial dates."
21KSE makes the following criticisms of this analysis and reasoning. It says that the reasoning involves a misunderstanding of the requirement for an "explanation" referred to in Aon; that it proceeds on the basis that it is necessary to characterise the explanation proffered as either "proper" or "not proper"; and that it treats an explanation characterised as "not proper" as determinative of the fate of the application and as "trumping" other relevant considerations. In relation to this last matter, reference was made to the statement of Gaudron J in Jagot v District Court (NSW) [1989] HCA 46; 168 CLR 23 at 76 in which her Honour described a discretionary power as generally one "exercisable by reference to considerations no one of which and no combinations of which is necessarily determinative of the result". Finally, it is said that the primary judge should have considered, as a factor to be weighed in the balance when exercising the discretion, that the amendment had not previously been made because of the inadvertence of KSE's legal advisers.
22As the plurality judgment in Aon makes clear at [102] and [103], the exercise of the discretion to allow an amendment necessarily involves a weighing process in which factors for and against the grant of leave must be identified and considered. Those factors include, if there has been delay in applying for the amendment, an explanation for the delay. At [103], it was said that the importance attached by Rule 21 (which is set out in Aon at [60] and is in similar terms to ss 56(1) and 57(1) of the Civil Procedure Act 2005) to the factor of delay "will require" in most cases that the moving party bring the circumstances giving rise to the amendment, and explaining the delay, to the Court's attention "so that they may be weighed against the effects of any delay and the objectives of the Rules". Those circumstances ought explain the delay, and in doing so may justify it, in the sense that they may provide reasons for it which are not consistent with any failure on the part of the moving party, or its legal advisers, to act diligently and expeditiously in the prosecution or defence of the relevant claim. If those circumstances provide some justification for the delay, for those or some other reasons, they may be weighed against the effects of the delay on the other parties, as well as on other litigants.
23The primary judge's observation, at [125], that there was "no proper explanation for the delay" is his assessment that the explanation proffered by KSE did not justify the delay, in the sense of being a factor which was able to be weighed against the effects of the delay and in favour of a grant of leave. This understanding of his Honour's observation is consistent with his earlier statement, at [116], that the material explaining the delay "does not justify it". None of this reveals any misunderstanding by the primary judge of the reason for any requirement for an explanation from the party seeking the exercise of the discretion. Nor does it proceed on the basis that it was necessary to characterise any explanation as being either proper or not proper. The primary judge used the latter description in this case as a shorthand way of saying that no good reason was put forward by KSE which provided some justification for the delay so as to be able to be taken into account in the balancing exercise necessary when exercising the discretion.
24The reasons at [125] do not indicate that the primary judge treated his assessment that there was "no proper explanation" as determinative of KSE's application. Having referred to the significance of the proposed amendments and to the absence of a satisfactory explanation for the delay, he considered a number of other factors which weighed against the grant of leave. His Honour did not in his analysis treat any one factor or combination of factors as "necessarily determinative" of the outcome of KSE's application. Finally, the primary judge did consider the explanation provided as a factor to be weighed when exercising his discretion. Having referred to the underlying evidence and his findings, he noted that the "only matter potentially favourable to KSE in this analysis is that I am not prepared to conclude that it deliberately held back" on making the amendment application: at [32]-[35]. That conclusion was the basis for his observations in [116] and [125]. The explanation was considered and given no weight as a factor in favour of leave.
25In our view, none of the criticisms made by KSE identify error on the part of the primary judge in relation to his consideration of KSE's explanation for the delay in making its amendment application.