Wouldn't the toddler be screaming and crying before she died? And the mother supposedly was able to sleep through it? I guess being passed out drunk isn't the same as sleeping though.
I have no kids, and I've never used a car seat, but every time I hear of these cases that involve toddlers and not infants, I'm always amazed that the child could not get out of the car seat by him or herself! Are they really that impossible for a toddler to figure out? Even if they are desperate? I guess even if they did manage to get out of the car seat, in many cases, they'd still be locked in the car, unable to unlock the doors. But in this case, maybe that would have been enough, if she could've roused her mother. How awful.