A more thorough explanation:

Definition: A testifier is someone who testifies or gives evidence in a court of law or in any other situation where their testimony is required. They are also known as witnesses. In the past, they were called testificators.

• The testifier was asked to swear on the Bible before giving their testimony in court.
• The police officer was a key testifier in the trial, as they had witnessed the crime taking place.
• During the hearing, the testifier provided crucial evidence that helped to solve the case.

These examples illustrate how a testifier is someone who provides testimony or evidence in a legal setting. They may have witnessed a crime or have information that is relevant to a case. Their testimony can be used to help determine the guilt or innocence of a defendant.