In keeping it real, there would likely be sone cctv footage that would identify him anyway. And Chesney saw him as well I think. Maybe not the stabbing part, but enough to give a good description to track him down.
It's a bad message to send though, to not identify a culprit, especially as it involves a serious assault, attempted robbery, and manslaughter/murder. Gemma will be able to tell the police who he is as well. I can't really see Craig's identification as a major factor. Corroborating evidence, sure, but not a make-or-break thing.