There is no way the mother would have known anything about Marcus at that time. So defending her because of some DM article that's out now is ridiculous. I don't think she's to blame for his death, that was nothing to do with her. But she was nasty and vindictive getting him jailed.
He lived in Tottenham fgs, of course he's going to know lots of people, some of whom may have become involved in gangs. Was he involved himself? I don't know and I don't care. It's irrelevant. To me it's always a tragedy when a teen dies, whether their actions contributed or not. They still have a family who will be utterly devastated.