Guardianship and administration applications in Western Australia often involve contested questions of mental capacity. In such cases, the State Administrative Tribunal (“the Tribunal”) must weigh lay evidence alongside professional assessments by medical and allied health practitioners. The recent decision in MM [2025] WASAT 103 provides a useful illustration of the principles the Tribunal applies when considering expert evidence.

Background: MM [2025] WASAT 103

The case concerned MM, a woman in her early 80s. Her daughter, YY, applied to be appointed administrator of MM’s financial affairs, alleging that MM lacked capacity and was the victim of coercion and elder abuse by her son, SS. Central to the dispute was whether MM had the ability to manage her financial affairs, particularly in light of a complex property transaction with SS.

YY arranged for MM to be assessed by a neuropsychologist, Dr J, who concluded that MM had a mild cognitive impairment and was unable to independently advocate for her interests in complex financial decisions. In contrast, MM’s general practitioner and a geriatrician (Dr F) found that MM had capacity to manage her affairs. Evidence was also provided by the Public Advocate and Public Trustee.

The Tribunal ultimately held that the presumption of capacity under the Guardianship and Administration Act 1990 (WA) had not been rebutted, and dismissed the application2025WASAT103.

The Presumption of Capacity

Section 4 of the Guardianship and Administration Act 1990 (WA) enshrines the presumption that every person is capable of managing their own affairs until the contrary is proved to the satisfaction of the Tribunal. As observed in Briginshaw v Briginshaw (1938) 60 CLR 336, clear and cogent evidence is required to displace such a presumption where serious consequences follow2025WASAT103.

In MM, the Tribunal emphasised that it will only be persuaded to override the presumption where the evidence is strong and consistent. Lay testimony, observed behaviour, and professional assessments all form part of this evaluative exercise.

The Tribunal’s Approach to Expert Evidence

The Tribunal is not bound by the rules of evidence (see State Administrative Tribunal Act 2004 (WA), ss 32(2), 32(4)) and may inform itself in any manner it thinks fit. This allows the Tribunal to consider expert reports while also taking into account the circumstances in which they were obtained.

In MM, the Tribunal noted several concerns with Dr J’s report:

MM did not understand the purpose of the assessment and was not given the opportunity to review key documents provided to Dr J by YY.
Dr J relied heavily on information supplied by YY, without equivalent input from SS.
The conclusions were inconsistent with the direct observations of the Tribunal, as well as the reports of MM’s GP, geriatrician, and the Public Trustee.

As a result, the Tribunal gave less weight to Dr J’s opinion, preferring the evidence of Dr F and others who concluded that MM retained capacity.

The Weight to Be Given to Expert Evidence

The decision underscores that while expert reports are often central to guardianship proceedings, the Tribunal will assess their independence, methodology, and consistency with other evidence before determining the weight to be attached to them.

As noted in XYZ (Guardianship) [2007] VCAT 1196, the Tribunal may consider evidence from a wide variety of sources, both lay and professional, when assessing capacity. In GC and PC [2014] WASAT 10 and LP [2020] WASAT 25, the Tribunal stressed that expert assessments are important but not determinative; they must be viewed in light of the whole factual matrix.

In MM, the Tribunal concluded that the difficulties MM experienced in advocating for herself were not caused by cognitive impairment but rather by family conflict and complex personal relationships.

The Right to Make Unwise Decisions

A further theme in MM was the Tribunal’s recognition that capacity does not equate to making only “good” decisions. As stated in T [2018] WASAT 128, people have the right to make bad or unwise decisions, provided they have capacity. In this case, even if some considered MM’s financial choices imprudent, the Tribunal found she was entitled to make them.

Lessons from MM [2025] WASAT 103

This case illustrates several important principles for guardianship and administration proceedings:

Expert evidence must be independent and fairly obtained. Reports arranged without transparency, or based on incomplete or biased information, may be given reduced weight.
The presumption of capacity is robust. It requires clear and persuasive evidence to be set aside.
Lay and professional evidence are both important. The Tribunal considers the whole of the evidence, including its own observations of the proposed represented person.
Capacity is not judged by the wisdom of decisions. Adults with capacity retain the right to make decisions others may consider unwise.

Conclusion

MM [2025] WASAT 103 provides timely guidance on how the Tribunal evaluates expert evidence in guardianship and administration cases. While expert reports remain a critical tool, their weight depends on independence, context, and consistency with other evidence. Above all, the case reaffirms the central principle that capacity is presumed, and only compelling evidence will justify interference with a person’s autonomy.