The abilities that most consistently appear to be relevant to a patient's capacity to make reasoned decisions regarding treatment fall into 4 categories.

- Ability to evidence a choice
- Ability to understand relevant information
- Ability to appreciate the situation and its likely consequences
- Ability to manipulate information rationally

Adapted from Briggs M et al. A handbook of healthcare ethics and institutional ethics for staff in healthcare institutions. Edmonton. The Bioethics Centre. 1994. Internet. Accessed on October 24, 2018.>