If Darlie (and supposedly Darin's) family do know she did it then I personally would find it somewhat easier to forgive Darlie Routier for a sudden overwhelming loss of control or whatever that she tries to cover up to save her own life given the position shes in, than a family that would willingly participate in a web of lies and have her lone little boy believe the same thing. They wouldnt be telling Drake the "well .... mommy did actually do this but for lots of good reasons and we have to keep it secret..." story, for fear of playground repitition. He would have got the "she's innocent, period" story.
We dont have the death penalty here but post partum depression is recognised in our law of infanticide - successfully evidence post partum depression and a woman would likely get a non custodial sentence for killing her own child under 12months. It wouldnt be a defence to murder in a child over 12 months, but it would be mitigating circumstances if there was a child under 12 months, i.e. that she was within 12 months of having given birth when the offence was committed. What is the relevance of the post partum depression thing over there? Had Darlie played this card would the end result have been different? If Darlie was British and had a long term sentence over here post conviction, if I was Darlie's Mom, I would be playing the post partum thing for all it was worth, becuase that would be a chance to go free early, rather than the hope of a quashed conviction on a few technicalities.