I'm not saying everyone would forget their children if they couldn't see them. The point I am making is that some parents might, if the car seat was facing backwards and the child couldn't be seen.
Lets say for example that Mom usually drops the baby off, but she has a meeting and Dad has to do it. He drives to work with the radio on and the baby is sleeping. Doesn't make a peep. He is distracted and forgets to go to the sitter. He just follows his usual rout, parks, locks the car and goes into the building, like he does every other day.
This never happened when the car seat was in the front seat. I used to be able to glance at my kids while I was driving when they were little, because car seats were still up front. I can remember singing along with the radio and being amazed that my 3 month old was trying to sing too.
I would keep a running dialog going about what was happening on the road. "Look at that car! he wasn't paying atttention to where he was going!" and other comments. As soon as the kids could talk, we could converse, and I could see them at all times, even out of the corner of my eye while I was paying attention to the road. I could give them a pacifier if they needed one. I could give them a bottle if they needed one, and I could tell when they needed to be changed, (had to pull over to do that!).
I think that a lot of these deaths are caused because the child is in the back seat, often facing away from the parent, and they can't be seen.
Lets say for example that Mom usually drops the baby off, but she has a meeting and Dad has to do it. He drives to work with the radio on and the baby is sleeping. Doesn't make a peep. He is distracted and forgets to go to the sitter. He just follows his usual rout, parks, locks the car and goes into the building, like he does every other day.
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But then he remembers that he needs to go pick her up after work? It takes him all flippin' day to remember...Nope, don't buy it...
I agree with your scenario. Add sleeplessness and fatigue of a new baby to the mix and it is even more likely.