A more thorough explanation:

Definition: Decessus (di-ses-uh-s), n. [from Latin decedere "to depart"]

1. Roman law. A death.
2. A departure.

This term has been used in both civil and common law, especially in reference to the desertion of a ground in a previous pleading in favor of another. See DEPARTURE.

Examples:

• When someone dies, it is referred to as a decessus.
• When someone leaves a place, it is also referred to as a decessus.

The examples illustrate that decessus can refer to both death and departure from a place. In legal terms, it can also refer to the desertion of a ground in a previous pleading in favor of another.