Answer:
It's because a person who witness' something, let's say in this case a murder, than the eye witness is the proof it happened if they say he murdered them or not. That person is the proof on the case, and it's important to have an eye witness when there are no fingerprints to be found. The eye witness can identify how tall they were, they're body figure, if they saw any facial features of the person, did they have facial hair, everything that involves appearance. An eye witness is able to identify.
Step-by-step explanation: