There is NEVER a justification for a crime... but there are reasons why they happen, and sometimes, these reasons are beyond the control of the guilty party.
Should they go free? No. Should they be killed? No... Should they be helped... yes. Punishing someone when they didn't have the proper Mens Rea (the evil intent) to commit the crime is just rediculous. Now, I'm not saying this is the case here.
An example (that I don't agree with) is when a husband rushes in a room, his wife is having sex... he loses it, kills them in blind rage. He's still convicted of murder, but 2nd degree/voluntary manslaughter (Depending on the jurisdiction)... and not 1st degree because he didn't have the intent... the malice... yes, he intended to kill, but through a cloud of blind rage.
Like I said, I don't like the idea of a woman who killed her kids to go free... but I don't that is the case... she is getting treated for her condition.
I am a big fan of rehabilitation rather than prison... throwing people away doesn't solve much... and makes them worse criminals...
I could rant on this topic forever.
C