The second criterion of credibility is the ability to see.

A witness who was in a good position to observe an event directly is, other things being equal, more credible than one who isn’t. No matter how reputatable or expert a witness is, if he couldn’t see what was going on then his testimony isn’t going to be much use.

Of course, this criterion is broader then just whether the witness has a good view of an event. In a disagreement about what someone said, this criterion would be satisfied by someone was there to hear; even a blind person can have an ‘ability to see’.

For this reason, some teachers talk instead of the ability to perceive. Even this is a little misleading. The basic issue is whether a witness is in a position to know that what they are claiming is true. Do they have direct access to the evidence, or are they speculating based on background knowledge, past experience, and instinct when they say what took place?