Definition - What does Eyewitness mean?
Eyewitness refers to any person who was present at the time of crime and has seen the event in such a way that they can be called in a lawsuit by any party to testify in court.
Justipedia explains Eyewitness
It is important for a person that stands as an eyewitness before the court to be legally fit to testify. This means that the eyewitness must be sane (mentally fit), not intoxicated, etc. If the eyewitness is not legally fit, their testimony will not be valued even if they are the only person who saw the crime taking place.