Purpose: The purpose of this paper is to consider the role of social work professional evidence in mental capacity law, specifically Court of Protection proceedings. The authors analyse how social workers perform as evidence givers in this domain and how social work as a profession is perceived alongside other professions within the context of adult social care decision-making in mental capacity law. Design/methodology/approach: This paper draws on textual evidence from judgments and existing empirical data published elsewhere. The authors consider the contribution of social work professional expertise to best interests decision-making in formal legal proceedings which, in turn, reflects on how social work expertise is relevant in everyday practice. Findings: The findings of this paper include that social workers are well placed to be experts on best interests decision-making in mental capacity law. However, the authors show that the Court of Protection has not always endorsed this form of social work expertise in its judgments, meaning that social workers can struggle to articulate an expert knowledge base. Originality/value: Overall, the authors conclude that social work evidence is incredibly valuable as expertise about the person’s best interests, particularly in the domain of welfare cases and care planning.

There is little empirical research focusing on how social workers experience the law in their everyday professional practice, and still less on how mental health social workers experience assessment for compulsory admission under mental health law. The article is informed by a hermeneutic phenomenological approach, drawing on in-depth interviews and practitioner diaries with social work Approved Mental Health Professionals (AMHPs), providing exploration of how social work AMHPs experience compulsory assessment under mental health law in practice. This is revealed as a socio-relational process, involving a focus on the person in their environment in relation to others, such as family and professionals. Ethical challenges realising human rights social work practice are illuminated. This draws attention to how space for such practice can be eroded by systems conditions. The importance of amplifying the voice of the person assessed is highlighted in the context that their voice is severely diminished during the process of assessment. The article provides insights on the complexity involved in compulsory mental health practice, drawing attention to trust as an important concept. Finally, the article argues that realising human rights-oriented AMHP practice requires social work to challenge systems conditions that erode the ability to do so.