Measuring mental capacity: a history


  • Dr Janet Weston

    London School of Hygiene and Tropical Medicine

Project summary

Formal assessments of mental capacity determine whether adults should make decisions regarding their own lives, and they are usually necessary when the person has impairments such as mental illness, learning disabilities and dementia. The courts of Britain and Ireland have been involved in assessing mental capacity for centuries, whether to appoint guardians or to overrule decisions made when capacity was absent. 

I will use these proceedings alongside medical, legal and advocacy material to consider how mental capacity was assessed, defined, and understood in the twentieth century, and to compare the approaches of different jurisdictions in light of their legal, medical and social contexts. 

My findings will cover the impact of changing medical knowledge and broader social attitudes towards disability and address the role of ideas regarding consent, medical ethics, vulnerability, autonomy and rights in determining how and when mental capacity should be measured.