[increment_i]

I'd imagine the purpose here would fall under general deterrence. By bringing down a harsh sentence here, you'd hope that future parents would take extra care to prevent such things from happening in the future. There is doubt just how effective general deterrence is in reducing criminal behaviour (see Death Penalty), but I'll admit it does call into question the utility of destroying a man's life that in all likelihood has already been irreparably altered. One thing is for certain, this guy was criminally negligent to highest degree (causing death), and it's unlikely a functioning criminal justice system is going to let someone walk away from that.