The general protections of the Fair Work Act operate on the basis of a statutory reverse onus of proof. In most legal cases the burden of proving the elements of the cause of action falls upon the Crown in criminal cases and the plaintiff or applicant in civil cases. However this is not the case in the operation of the general protections, as is neatly explained in this extract from a recent decision of the Federal Court of Australia.
“Section 361 is a reverse onus provision. It provides that where it is alleged that a person took or is taking action for a particular reason or intent, and where that reason or intent would constitute a contravention of Part 3‑1, it is presumed that the action was or is being taken for that reason or intent, unless the person proves otherwise. Section 361 does not remove the need for an applicant to establish the objective facts which form the basis of the respondent’s conduct: Tattsbet Limited v Morrow  FCAFC 62; (2015) 233 FCR 46 at  (Jessup J, Allsop CJ and White J agreeing). The rationale for the s 361 presumption is that the reason for taking action is a matter that lies peculiarly within the knowledge of the person taking the action: Celand v Skycity Adelaide Pty Ltd  FCAFC 222; (2017) 256 FCR 306 at , citing, amongst other authorities, General Motors-Holden’s Pty Ltd v Bowling (1976) 51 ALJR 235 at 241.”
Australian Building and Construction Commissioner v CoreStaff WA Pty Ltd  FCA 893 delivered 26 June 2020 per Banks-Smith J