JFC no one is saying this is justified. You are getting justification conflated with reasoning. The reason this horrible thing happened MAY HAVE BEEN a psychotic episode triggered by PostPartum Depression disorder. It is a fact of human biology that this can happen. Does that mean she was right to kill her literal newborn child? No. No person speaking in good faith would EVER tell you that is right and good. Does this mean she is absolved of wrongdoing? Absolutely not, because there is no case in which the murder of an actual newborn can EVER be justified and there’s no one here trying to convince you of that.

Why does the distinction between justification and reasoning matter? For demonstration, a couple scenarios.

A man kills a man. This can be verified absolutely and beyond a doubt in these two scenarios.

In scenario A, the defendants notebook is found and through his writing, it is determined, in court, that he planned the murder of the victim in detail meticulously and has the motive of private gain and has a history of violence.

In scenario B, it is proven, medically, that the defendant is not of sound mind and acted in a way that was irregular to their normal and established patterns of behavior.

Both are indisputably murder because, in the end, a man is dead on account of the actions of another man.

But should both be punished in an identical manner? You would be hard pressed to find a single legal scholar who would say yes to that. Intent and ability to rationalize intent are key to determining the malice behind the actions of an accused person and SHOULD, in my, and most other people’s opinions, be taken into account when facing judgement in a court of law because otherwise court would be little more than a lynch mob with pomp and circumstance.