Here’s some comments I wrote in 2009, comparing the reverse onus in the (then new) Fair Work Act and its predecessor provision in the Workplace Relations Act, with the current situation for discrimination claims.
The current section 809, in relation to freedom of association, and section 664, in relation to unlawful termination, of the Workplace Relations Act, effectively shift the burden of proof to (for the purposes of our discussions) the employer, by including a presumption that the conduct (ie the termination or relevant freedom of association conduct) was carried out for a proscribed or prohibited reason.
The Fair Work Act contains a similar presumption in the General Protections Part …
The Act, by that provision, puts the onus on the employer to prove the reasons for the action did not include a discriminatory reason. A mere denial may not be sufficient.
The employer has to prove that to the civil standard. That is they have to prove that on the balance of probabilities, the discriminatory reason was not one of the reasons for the adverse action.
This ‘reverse onus’ goes some way to mitigating the difficulty faced by the complainant.
The employer will usually be better placed to lead direct evidence about the reasons for the adverse action. As has been recognised, this is something peculiarly within the knowledge of the employer.
The employee’s evidence will be about what the employer purported to be the reasons for the adverse action, and also, and generally more importantly, about facts and circumstances that cast doubt on any assertion by the employer that the reasons did not include a discriminatory reason.
In the absence of the reverse onus, the employee would be at a very significant disadvantage. The reverse onus goes some way to redressing that imbalance.
The operation of the reverse onus is considered in Galvin v Renito Pty Ltd. In that case Ryan JR applied the reasoning of Moore J in Stojanovic -v- The Commonwealth Club Ltd to the operation of the then s 170CK of the Workplace Relations Act:
28 His Honor adopted a formulation of the onus on the employer approved by the High Court of Australia in General Motors Holden Pty Ltd -v- Bowling and expressed by Mason J when addressing s5(4) of the Conciliation and Arbitration Act 1904, an earlier predecessor s170DF and s170CK. At 617 Mason J referred to the onus on the employer of establishing affirmatively that it was not actuated by the reason alleged in that case in the charge laid under s5. He held that the consequence was that the employee, in order to succeed, was not bound to adduce evidence that the employer was actuated by that reason, a matter peculiarly within the knowledge of the employer. He found the employee was entitled to succeed if the evidence was consistent with the hypothesis that the employer was so actuated and that hypothesis was not displaced by the employer. He said:
“To hold that, despite the subsection, there is some requirement that the prosecutor brings evidence of this fact is to make an implication which, in my view, is unwarranted and which is at variance with the plain purpose of the provision in throwing on to the defendant the onus of proving that which lies peculiarly within his own knowledge.”
In Greater Dandenong City Council v Australian Municipal, Clerical and Services Union, in dissent, Finkelstein J expressed the view that the presumption in the predecessor to new s 361 did not arise where there is sufficient evidence to enable the court to make a positive finding whether conduct has been carried out for the alleged reason or with the alleged intent. This seems consistent with the general approach to the ‘reverse onus’. It is a presumption that arises if the claimant’s evidence doesn’t establish a positive case.
As earlier commented, this reverse onus seems to go some way to redressing the imbalance that inevitably arises in a case directed towards establishing the reason or reasons for particular conduct.
In contrast to the foregoing, there is generally no similar presumption in anti-discrimination legislation. (Save that in cases of indirect discrimination, if the respondent says that the discriminatory term is reasonable, it is for the respondent to prove that reasonableness.)
This is an important difference between the two types of claims. A complainant in an anti-discrimination legislation claim would have to demonstrate that the reasons for the less favourable treatment include the attribute, and that is of course fairly difficult. It necessarily relies on evidence as to the facts and circumstances which support the proposition that the conduct was because of the attribute. In contrast under the new Fair Work Act, it will be for the employer to prove that its reasons did not include a discriminatory reason.
… a complainant may find a claim under the Fair Work Act less onerous because of the presumption in their favour and the absence of the statutory requirement to point to the treatment that would have been afforded to a hypothetical comparator.
However, in could be argued that there will be little practical difference in running the employee’s case because:
a) notwithstanding the reverse onus, the complainant will usually have to bring evidence to contradict the employer’s evidence as to the reasons for the adverse action – that is, if the employer leads evidence that the reasons were other reasons, which did not include sex / race / age / disability etc, then that evidence, if uncontested or if otherwise accepted, would likely discharge their onus and the employee’s claim will fail;
 Johns v Gunns Ltd (1995) 60 IR 258
 Randall v Greyhound Australia Pty Ltd  FMCA 1191
 General Motors Holden Pty Ltd -v- Bowling, referred to below
 Heidt v Chrysler Australia Ltd (1976) 26 FLR 257
 FCA 1005
 (Industrial Relations Court of Australia, unreported, 8 December 1995)
 (1976) 12 ALR 605
  FCA 349 (4 April 2001)
 At paragraph 219