Must finding of psychological / psychiatric condition be founded on expert evidence?

A delegate cancelled the Applicant's visa under s 501(3A) of the Migration Act 1958 (Cth), after which the Minister personally decided under s 501CA(4) not to revoke the cancellation. The basis for the non-revocation was the Applicant's convictions for child pornography.

In making the non-revocation decision, the Minister wrote as follows:

33. In my opinion the fact that Mr RENTON’s previous sexual offending against an underage person, and that more recently over a prolonged period he organised child abuse material, stored it systematically on various devices and made it available to others with similar interests and admitted to police that he accessed the images for ‘sexual gratification’ demonstrate that he has an ongoing sexual interest in children. I have had regard to and concur with the Judge's comments that he has a ‘limited but telling criminal history’ and that his ‘antecedents reflect sexual issues dating back 30 years’. I am concerned that despite the experience of being tried for these crimes, hearing the comments of the Court when sentencing and receiving substantial terms of imprisonment, Mr RENTON has failed to acknowledge he has psychological sexual issues relating to children. In my opinion Mr RENTON’s attribution of his protracted and repeated access and distribution of child pornography to ‘voyeurism’ demonstrates his insight into his offending and its impact on the victims is inadequate and not fully appropriate.

...

38. I acknowledge Mr RENTON's guilty plea and find this weighs in his favour. However, I am also mindful that by pleading guilty Mr RENTON obtained a 25 per cent discount in sentencing from the Court.

Some of the questions to the Federal Court (FCA) were as follows:

Question 1: Can it be said that "a requirement that a positive finding or inference of fact that is of central importance to, or which is a critical step in the Minister’s reasoning be supported by some at least some material, is an aspect of the condition implied by common law rules of construction upon the exercise of the Minister’s function under s 501CA(4) of the Act that the Minister must act reasonably in the manner in which the decision-making function is discharged"?

Question 2: Does the 'no-evidence' ground of judicial review mean "not a skerrick of evidence"?

Question 3: In the context of administrative law, must a finding that there is a psychological or psychiatric condition be founded upon expert medical or psychological evidence?

Question 4: Was the Minister’s reference to the Applicant’s "psychological sexual issues" a "statement that involved the application of specialist expertise" or that "was not open absent a specialist diagnosis"?

Question 5: Was the Minister's obligation to afford the Applicant procedural fairness a "condition of the lawful consideration of whether to revoke the decision to cancel the applicant’s visa pursuant to s 501CA(4), and arises as a matter of implication through the application of common law principles of statutory construction"?

Question 6: Can it be said that "the only expert evidence before the Minister was that the applicant had no psychiatric disorder, and that for these reasons, the Minister’s conclusion was not obviously open on the known material", with the result that the Minister failed to afford the Applicant procedural fairness?

Question 7: Can it be said that "to take account of the fact that he had received a 25% discount in sentencing from the court was to take into account an irrelevant consideration"?

The FCA answered those questions as follows: