Ok, I do want to say something, Only because I do know this has accidently happened. I know once, in a hurry, we started to back out, without having our son fully buckled, (but we caught it rather quickly) And it was a complete accident.
While I do believe that it wasn't the case, if it was, I would think the death of the baby is alot already. However, as they stated what they were charging her with, I agree with. she was on a cell phone, and wasn't paying attention. (this is why if you have a freakin cell phone and your driving, use a headset, or bluetooth, or freakin use the speaker phone feature. So yes the grandmother most definately was at fault for that. I know I have caught my mom putting in my kids in their seats and it was the correct way. Which is usually why I put my kids in myself rather than allowing them to if I am there.
But I also know that when I had my first son ( I was 20 years old) I asked my mom ALOT. nothing on car seats though, because apparently, I didn't even have a car seat as a baby. (Glad I survived) . I agree with what others have said though, the reason why a 16 year old shouldn't have children, is because they really aren't ready, and she did care enough to have the baby, bbut its rare that a 16 year old does know exactly what they are doing. Not saying that they all can't or aren't good mothers, but they look to their mothers for help, so it really should all fall on the grandmother.
Either way its horrible that it happened.