What term describes a person who sees or hears an event, particularly a crime or accident?

The term that accurately describes a person who sees or hears an event, particularly in the context of a crime or accident, is "witness." A witness provides firsthand testimony about the events they observed, which can be crucial in investigations and legal proceedings. Their account can help establish facts and clarify what occurred.

While an "observer" might also be someone who watches an event, it does not specifically encompass the legal implications or responsibilities associated with witnessing an event that may involve a crime. A "suspect" refers to a person believed to be involved in the commission of a crime, while a "victim" is someone who has suffered harm due to the actions of others. Thus, these terms do not fit the definition of someone who merely sees or hears an event.