I was part of a mock trial for a friend of mine in law school. Part of it was that I was "attacked" by someone in a well lit alleyway. I knew it was going to happen and how it was going to happen. She approached me, bumped into me, started yelling at me, and I started yelling back, and then she sprayed something in my eyes (water, but it was supposed to be something more caustic). After that she ran off and I found a nearby police officer to report the crime.
They caught her and had me do a line up where I successfully identified her. A few weeks later they had the trial where I sat on the witness stand, got cross examined, and identified her as the attacker. I was completely positive it was her.
Well, as it turns out, it wasn't her. It was someone who looked similar, but she was actually a couple inches shorter. When I was attacked she was wearing a hoodie. I was so positive though. I was sort of floored. I knew the attack was coming. I knew it was fake. And I knew that I'd have to identify her after the fact. Yet I totally messed it up. I can absolutely see how eye witness testimony cab be extremely inaccurate in the case of a real crime being committed. We think we have photographic memory but the brain fills in a ton of things that we're not aware of.