This article is part of the Iris Ethics Knowledge Base; you can find a directory of all articles here.
Overview
These worked examples show how the National Statement's consent framework applies to complex or non-standard consent scenarios. Each is a hypothetical, generic scenario; it does not describe a real Iris Ethics application.
Case study: Research with participants who have fluctuating capacity
Description: A research team proposes interviews with people experiencing episodic mental illness (bipolar disorder) about their experiences of mental health services. Participants may have full capacity at some times and reduced capacity at others.
Key considerations: The National Statement recognises that capacity to consent may fluctuate, and that even without full capacity a person may retain some understanding of the research and its burdens and benefits (NS 2.2.12). The protocol must specify how capacity will be assessed at each point of contact, what happens if a participant loses capacity during or between data collection points, and what happens to data already collected if a participant subsequently loses capacity. NS Chapter 4.5, which applies to people experiencing physical or mental ill-health, requires that inclusion and self-determination of participants remain paramount in the research design. The consent form should address these scenarios explicitly. See When consent can be modified and People with disability or illness (NS 4.5).
Review pathway: Full HREC review, given the vulnerability of the population and the sensitivity of the topic. Key issues: capacity assessment protocol; data handling on capacity loss; welfare safeguards.
Case study: Opt-out consent in a large administrative dataset study
Description: A public health research team proposes a study using a government administrative dataset. The custodian has agreed to provide a de-identified extract. Individual consent from the 500,000 individuals in the dataset is not practicable.
Key considerations: If personal identifiers have been fully removed prior to the researchers receiving the extract, and the researchers agree not to attempt re-identification and to take reasonable steps to prevent it, the research may qualify for exemption from ethics review under NS 5.1.17(a). If the dataset remains re-identifiable, even without directly identifying fields, the research involves personal information, and NS 5.1.16 prevents exemption in that case: a waiver of the requirement for consent must instead be sought from an HREC under NS 2.3.9–2.3.10. An opt-out approach (NS 2.3.5–2.3.8) is a separate alternative, available only where it is feasible to contact participants but explicit consent is impractical given the scale of the project; it is not available once contact is no longer feasible, as in this scenario. See When consent can be waived, Opt-out approaches and Exemptions from ethical review (NS 5.1.15-5.1.18).
Review pathway: Exemption assessment or full HREC review for a consent waiver, depending on the identifiability determination.
Case study: Limited disclosure in a mystery shopping study
Description: A market research firm proposes a mystery shopping study assessing customer service quality across a retail chain. Frontline staff are not told which interactions are part of the study, as advance notice would change their behaviour and invalidate the findings.
Key considerations: This is limited disclosure without active concealment or planned deception directed at the staff being observed as incidental subjects of the research. Where limited disclosure of this kind is proposed, the applicant must show there is no alternative involving fuller disclosure, that the benefit justifies the limited disclosure and any risk to trust in research, that the research involves no more than low risk and is unlikely to affect participants adversely, and that the extent of the limited disclosure is precisely defined (NS 2.3.1). Where the design instead involves active concealment or explicit deception of staff, for example fabricated shopper identities designed to elicit particular behaviour, additional safeguards apply and only an HREC can approve the research (NS 2.3.2 and 2.3.4). See Limited disclosure and deception.
Review pathway: Lower risk review where disclosure is merely delayed and risk is low; full HREC review where active concealment or deception is involved.
Related resources
This page was last updated on 16 September 2026.
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This article makes reference to the National Statement on Ethical Conduct in Human Research 2025. It is intended as practical guidance and does not constitute legal advice.
AI Disclosure: Resources in this library were prepared using Large Language Models with input from Iris Ethics staff who guided the scope and design. Subsequent revisions and final versions were developed and approved by Iris Ethics staff.