Blue, then why go to trial? Sincerely, I really mean that. Why bother with a trial if everything needed to send him for life in prison/death penalty is already fully known and agreed to by all parties?
He's already admitted he left his baby in the car all day in the heat, and now the baby has died.
Those facts are not in question, at all, and if all you need are those facts everyone would agree he's guilty as charged.
But that's why we have juries. So they can look at it and see mitigating factors. He has not pled guilty to the crime - but has in fact, agreed that he's guilty of the very minimal tenets of the crime he's being charged with.
This is where juries come in. And sometimes, they go all the way to a "jury pardon" - meaning yes he's guilty as charged but due to the circumstances shouldn't be punished to that degree.
Whether they admit it or not, jurors if this comes to trial will be considering intent.