>They did not intend to kill the baby <
Neither do people who shake babies to death. They are trying to get the baby to stop crying.
However, in both situations you end up with a dead infant. Ignorance (especially of that magnitude) of the law is no excuse.
When I said
“if they had only been stupid they would have taken the kid to the doctor”
I was indicating what they did was not just ignorance but criminal..