I'm a prosecution witness in a trial. What should I expect?

A good defense attorney will ask you mostly close ended, leading questions (formed more like statements than questions) that require no more than a yes or no answer. Listen carefully to the question she is asking and answer accordingly. If the yes or no needs explanation based on the way the question was worded to you, explain after giving the yes or no answer. In a case like this, she will most likely attempt to attack your identification and ask questions about things like lighting, opportunity to view your attacker, the height of your attacker, etc. If her client's physical description varies from what you originally told police, she will ask about that as well. Based on what you have said about the facts, the identification is about all she can attack you on as the police did the rest of the work in finding him. If anything you say on the stand in direct examination is different from anything you said before (no matter how slight it may seem), she will most likely ask about that as well. As I said, in a case like this, where much of the evidence leading to the guy came from the police investigation, she will most likely be going after them much stronger than she will after you. If she's smart, she will try to make your identification appear to be a honest mistake. . .at least that's what I would do.