A more thorough explanation:

An earwitness is someone who testifies about something they heard but did not see. They have firsthand knowledge of an event from hearing it. Earwitnesses are often called to court to give testimony about what they heard.

For example, if someone is a victim or witness of a crime, they might not get a clear view of the suspect. In cases like telephone fraud or blackmail, the sound of the suspect's voice might provide the only clues to their identity. In such a situation, the police have to rely on earwitnesses, rather than eyewitnesses, for evidence. The earwitness will be required to describe what the voice sounded like and may be asked to try and identify the suspect from different voices.

However, relying solely on an earwitness's opinion can be problematic. In Palmer v. Peyton, the court held that the voice of a suspect can be evidence of their guilt, but it is not always reliable. Misidentification is a possibility, which weakens its strength as proof of culpability. In Long V. Dutton, the court held that earwitness identification, like eyewitness identification, presents a substantial likelihood of irreparable misidentification.