You don't understand what having a child under the age of six months is like. You are incredibly sleep deprived, making errors at work and are a danger on the road. My wife and I piled up a barricade of boxes to the door of our balcony because we were terrified that one of us would hallucinate at 4am and drop our newborn off the fourth floor.
So when I read about a mother who thought she had dropped her infant off at daycare with her four-year-old, and instead found her dead in the backseat when she got off work that night, my first thought was, "That could have been me." When I read about a parent who backed her car over her infant, I immediately remembered the morning I backed over my lunch because I had been up all night with a screaming newborn and my morning routine got off a beat when my neighbor interrupted it to ask a question.
The real tragedy here is that we could probably greatly reduce these incidents by giving new parents extended maternity leave or providing them some other form of social support. Unfortunately, the same mindset in this country that considers these tragedies "criminal" are also the same people who think giving a new mother time off is some kind of free ride.
If you read stories about these tragedies and your gut reaction is "shitty parents" who "want to kill their children," then your ethical mindset is completely alien to me. I don't know how to teach you the importance of compassion and sympathy for your fellow human beings.