Memory- who should be an eyewitness

Knowing now the difficulties presented in achieving reliability in eyewitness testimony, what sort of guidelines should be created for those allowed to testify as an eyewitness? For example, how young of a child can be considered a reliable eyewitness? What if a four-year-old was the only witness to a crime? Should they be allowed to testify? How much credence could be given to their testimony? Can the visually impaired serve as eyewitnesses? Can they observe information that would be useful other than seeing things? How reliable is that information if they couldnt see who was doing what? What other guidelines do you think should be imposed?

Writing assignment should be 250 words.