This article considers the place of service-user knowledge and expertise within an evidence-based practice perspective. It makes a strong argument that client involvement is a core principle of Sackett et al.'s foundational approach in evidence-based medicine. In so doing, it draws on research on service-users' perceptions and experiences of evidence-based practice.

For service users, evidence-based practice lacks relevance and trustworthiness unless it explicitly factors in the expertise of service users themselves. Evidence-based practice is seen to have merit as a tool for enhancing accountability, but service users see a role for themselves at individual and representative levels in the process of evidence-based practice. They place a high value on the expertise derived from lived experience, and recognise that fluctuations in capacity and changes in circumstances of many service users require a flexible approach to their participation in decision making. A pragmatic approach to the conceptualisation of evidence is recommended, which not only maintains scientific rigour inherent in evidence-based practice but also more strongly emphasises the process of analysing evidence appropriate to a particular individual's preferences and circumstances.

For human service practitioners, this study emphasises the need to develop professional skills in assessing the capacities, circumstances and preferences of clients and analysing and applying evidence for practice in ways that conform to a client-centred approach. It also indicates a need for researchers and practitioners to recognise and value service-user expertise.