Legal Definitions - non sui juris

Non Sui Juris describes an individual who, for legal purposes, does not possess the full ability to manage their own affairs, make independent decisions, or enter into binding agreements. This status typically arises when someone is either below the legal age of majority or has been determined by a court to lack the mental capacity to understand and make sound decisions for themselves.

Here are some examples illustrating when an individual might be considered non sui juris:

• Example 1: A Minor Entering a Contract

  Imagine a 16-year-old who wants to purchase a new smartphone with a two-year service contract. Because the individual is under the legal age of majority (typically 18 in most jurisdictions), they are considered non sui juris for contractual purposes. This means they generally cannot legally enter into a binding contract on their own. The phone company would likely require a parent or legal guardian to co-sign the agreement, or the contract could be voidable by the minor once they reach adulthood.

• Example 2: An Adult with Advanced Cognitive Impairment

  Consider an elderly person diagnosed with advanced Alzheimer's disease who can no longer recognize family members, manage their finances, or understand complex medical instructions. If a court determines that this individual's cognitive impairment prevents them from understanding the consequences of their actions, they would be declared non sui juris. A court-appointed guardian or conservator would then be responsible for making legal, financial, and healthcare decisions on their behalf, as the individual lacks the legal capacity to do so themselves.

• Example 3: An Individual Under Court-Ordered Guardianship

  Suppose an adult with a severe intellectual disability has always required significant support for daily living and decision-making. If this individual inherits a substantial sum of money, a court might find them to be non sui juris due to their inability to manage complex financial matters or protect their own interests. A guardian or trustee would be appointed to manage the inheritance and other legal affairs, ensuring the funds are used for the individual's benefit, because the individual lacks the legal capacity to manage it independently.