It is my personal opinion that a "parent" would never "forget" about the a child in a vehicle. It makes no difference if it's out of their "routine" or not. An excuse is not good enough for just plain murder.
There is not an excuse in the world that can justify it. Just like anybody else that hurts child, death.
So every person whose kid drowns in a swimming pool is also a murderer? Because it's so easy to avoid, it should never ever ever happen right? No room for error right? Same thing.
But, for you, there's no gray area, instant death penalty for the parent. Just doesn't make sense to me.
Apples and Oranges