I have worked a couple accidental deaths that were exactly like that.
Mom lays baby down with her, then rolls over on the baby and suffocates it, all in an either drug or alcohol induced stupor. Truly sad.
If you all remember, Dad said Mom was asleep on their bed with her son when he came home after 4:00 a.m. I wonder if the baby had ALSO been on the bed...
It is sad.