Conclusions
51 In my view, the Tribunal made no finding, either explicitly or necessarily implicitly, that the evidence of the doctors was 'flawed'. Nor, as a matter of law, was it required to do so. The Tribunal merely found that, taking into account all the evidence, the respondent had considerably understated the incidents at ADFA to his doctors. The evidence (including that of the respondent's parents) which the Tribunal accepted suggested that what occurred at ADFA was more serious. The Tribunal then assessed the medical evidence in the light of what it considered to be the true history. That history was considered by the doctors whose opinions were evidently most valued by the Tribunal. It seems that Drs Canaris, Lee and Nielssen all accepted a causal link on the relevant history. That history was one of stressful military training experiences and a degree of harassment.
52 A decision-maker such as the Tribunal, at least one not bound by the rules of evidence, is entitled to reason logically and to draw inferences from expert opinions before it. In the course of an administrative inquiry (or of curial litigation) it is often practically impossible (particularly having regard to the desirability of maximising expedition and minimising expense) to ensure that every potentially relevant item or version of the history is put before a medical or other expert witness. Non-expert decision-makers should, of course, exercise due caution as to matters the subject of, and concerning, expert opinions: the subject matter at hand may, upon some difference in the history emerging, bring more or different matters into focus for an expert than for a non-expert; further, if the decision-maker introduces a new view of the facts without proper notice to the parties, a denial of their right to be heard may occur. Subject to such matters, however, decision-makers are not obliged to leave their capacity for reasoning and drawing inferences behind them when they come to deal with the evidence of expert witnesses. Where, as here, the Tribunal includes a member with a medical background, a conclusion that the permissible scope of the drawing of inferences as to medical matters has been exceeded should not be readily reached by a supervising court. Nor does it appear that the Tribunal's reasoning could properly be said to have taken either of the parties by surprise, so as to constitute a denial of procedural fairness.
53 In argument, counsel for the Commission placed much reliance on Rodriguez v Telstra Corporation Ltd [2002] FCA 30, (2002) 66 ALD 579, a decision of Kiefel J. The facts in that case were significant. The AAT, including a medically qualified member, without any medical evidence on relevant questions, concluded that an employee's admittedly 'ongoing major depressive disorder' had ceased to be caused by certain potentially compensable factual events and had become instead, caused by other, non-compensable events. This was because the employee had, after a time, complained to doctors less of the compensable events than of the non-compensable events. Her Honour said:
'… If the tribunal did act upon the medical opinion of one of its members it did not state this. In any event if a view is formed by a tribunal which goes beyond the opinions expressed by the experts in evidence, fairness requires that it be disclosed and the parties permitted an opportunity to address it. …
The tribunal is not bound by the rules of evidence (s 33 of the Administrative Appeals Tribunal Act 1975 (Cth)) and may inform itself in such a manner as it thinks appropriate. This does not mean that the rules of evidence are to be ignored. The more flexible procedure provided for does not justify decisions made without a basis in evidence having probative force …The drawing of an inference without evidence is an error of law … Similarly such error is shown when the tribunal bases its conclusion on its own view of a matter which requires evidence. In Collector of Customs (Tasmania) v Flinders Island Community Association (1985) 7 FCR 205 at 210; … a Full Court of this court held that it was unjustifiable, and therefore legally erroneous, for a tribunal to base its conclusion upon its own understanding of traditional aboriginal concepts of community ownership and interests, in the absence of any evidence on the matter.
It may be said that expert evidence is sometimes over-utilised and is called in situations where an arbiter of fact is in a position to determine the matter for itself. Sometimes all that is necessary is for a method or process to be explained, so that the court or tribunal can then apply it to the facts it finds. On the other hand, there are cases where a whole question is, in effect, relegated to experts to give evidence upon it. This was such a case. The tribunal was not put in a position where it could simply draw its own inferences. In an area which required an understanding of a disorder it could only receive the opinions, have the bases for them explained if they differed and apply logic to determine which were to be accepted.
Given my view as to the need for expert medical opinion on the topic, it is not necessary for me to consider the balance of the tribunal's reasoning. …'
54 I do not, with respect, disagree with anything that fell from her Honour. It is to be remembered, however, that her Honour was writing in the context of the case before her. This, by contrast, is not a case in which the Tribunal has '[gone] beyond the opinions expressed by the experts in evidence': the Tribunal merely accepted some of those opinions over others and logically applied the logic and doctrines inherent in those opinions to a history of disturbing events at ADFA that, in general, was even stronger than that which at least some of the doctors had had. There was a basis for the Tribunal's decision in evidence that had probative force. In the circumstances, the Tribunal did not commit the error of basing its conclusion on its own view of a matter which, being expert, required expert evidence. The question whether the respondent had continuing, if recurrent, depression and whether any such continuing depression was still caused by his time at ADFA did need expert evidence, but there was ample evidence of that kind before the Tribunal. The Tribunal was, by that evidence, put in a position where it could infer that the correct history, as the Tribunal perceived it, provided even stronger reasons than some of the doctors had for answering those questions favourably to the respondent.
55 In my view, there was sufficient of the accepted history put before the current medical witnesses to justify the Tribunal's acceptance of the opinions it preferred.
56 The separate claim that the Tribunal substituted its own opinion on causation should also be rejected. Again, the Tribunal's conclusion must be read in the context of the reasons as a whole. It is tolerably clear from the entirety of those reasons that the Tribunal's reasoning relied on the medical evidence before it. It is permissible to discriminate between expert witnesses on the basis of their appeal to the informed lay decision-maker's sense of the probabilities: Repatriation Commission v O'Brien (1985) 155 CLR 422.
57 As the Tribunal noted, Prof. Tennant, in cross-examination, said that significant stressors had occurred whilst at ADFA and they contributed to the respondent's depression experienced after discharge, but that most stressors were short lived, unless there were a degree of underlying pre-existing vulnerability. The Tribunal also noted that the Professor had previously found that the respondent had a pre-existing genetic vulnerability to depression. The Tribunal acknowledged the necessarily stressful environment of ADFA, including, by implication, that the respondent had been subjected to 'behaviour designed to humiliate and demean or what amounts to nothing more than pointless excuses to punish'. The Tribunal also recorded its finding, as set out in [44] above, that the Navy acknowledged that the respondent was psychologically unsuited for entry into ADFA but enlisted him in order to make up numbers.
58 The Tribunal then said that the 'inevitable result of what the [respondent] experienced at ADFA has been psychiatric illness including depression which still continues'. In drawing this conclusion, the Tribunal was not, in my view, substituting its own opinion, and/or formulating its own opinion as an expert witness, regardless of the actual evidence on causation. The Tribunal had previously stated that it preferred the evidence of the psychiatrists who had examined the respondent most recently: Dr Canaris, Dr Nielssen and Prof. Tennant. Dr Canaris was of the view that evidence for a persisting, albeit attenuated, causal link between ADFA experiences and current symptoms would exist if the account given on behalf of the respondent of his behaviour was accepted. Dr Nielssen conceded that the respondent's current depression was recurrent and could have as a contributing factor the initial stressors at ADFA. Further, Dr Nielssen agreed that the stresses of ADFA could be a contributing factor to a psychiatric illness later developed by a vulnerable person, unfit to have been at ADFA, such as the respondent. It can be seen that, on that evidence, combined with Prof. Tennant's opinions (set out above in [39] and in [41] particularly), the conclusion of a causal link between the respondent's employment at ADFA and his psychiatric illness including depression was well open to the Tribunal on the evidence.
59 The Commission argued that, despite these comments in cross-examination, Dr Nielssen and Prof. Tennant had not resiled from their earlier views to the effect that any contribution by his ADFA experiences to the respondent's mental problems was, in the main, short-lived. However, Prof. Tennant's evidence appears to have been more complex than that, acknowledging, for example, that an initial stressor causing depressive disorder could make the patient more susceptible to recurrence of depression from later stressors. Dr Nielssen conceded that the initial ADFA stressor was a contributing factor to the respondent's recurrent depression and that there was 'quite often a co-morbidity with depression and dysmorphic disorder'. The Tribunal had the benefit of viva voce evidence from the doctors. What weight it gave to their evidence or to different parts of it was a matter for the Tribunal.
60 In any case, the submission that the Tribunal simply created and applied its own opinion was predicated on the premise that all the medical evidence was flawed because of the difficulties about the histories the doctors had. As I have indicated (at [51] above), I do not accept that premise.
61 No error of law appears to me to have been shown. Accordingly, Grounds (a) and (e) fail.