A more thorough explanation:

Capacity refers to a person's ability to make a rational decision based on all relevant facts and considerations. In legal contexts, capacity can have different meanings:

In criminal law, capacity means that the defendant must have the ability to understand that their actions are wrong. For example, if someone commits a crime but they did not understand that it was illegal, they may not be held responsible for their actions due to lack of capacity.

In contract law, capacity refers to a person's ability to enter into a binding agreement. To have capacity, a person must meet certain requirements, such as being of a certain age and having a sound mind. If someone lacks capacity when they sign a contract, the contract may be void or voidable.

In the context of wills, the maker of a will must have testamentary capacity. This means that they must be of sound mind and understand the consequences of their decisions when making a will. If someone lacks testamentary capacity when making a will, the will may not be valid.

For example, if someone is suffering from a mental illness that affects their ability to make rational decisions, they may lack capacity in the context of criminal law or contract law. Similarly, if someone is elderly and suffering from dementia, they may lack testamentary capacity when making a will.