I was once a witness to an armed robbery in our restaurant, and I did get a good look at the suspect's face before he left with the cash. I got a call three days later from a detective who wanted me to look at a photo array lineup. I was relieved I wasn't going to have to do an in-person lineup with that criminal just a few feet away from me. I managed to pick the guy out of the photo lineup because he had a swastika tattoo on his forehead.
I don't ever want to go through an experience like that again, but I was glad I could confirm the detective's suspicions with a positive ID.