Psychosis and depression are two entirely separate conditions. This what exhaustively dealt with during the aftermath of Adrea Yate's murders, and post-partum depression is simply not violent. Various dishonest feminists just make that claim.
Using it to "defend" murder is not the same thing as saying that post-partum mental illness should be cared about. If you care about this murder you should care about whether she had post-partum depression.
That is wrong. Post-partum depression is not in itself violent.
Then maybe you might be able to step in and save someone you know or love. It can happen to any mother.
Oh, yes, every mother is a potential killer. /sarcasm
Frankly, I think that state of mind can be a mitigating factor in prosecution of crimes; in the court system it is as a matter of law. Disordered and irrational thinking that a killer has no insight to, is not as heinous a murder as a cold-blooded decision to punish a mate, or collect insurance money, or keep a boyfriend that doesn't want children.
Sure, state of mind is a factor because we are always looking for ways to let a murderer walk. Society hates children, so mudering moms get a pass on whatever a dishonest lawyer and a paid feminist "expert witness" can make up on the fly. When that works to get the murdering skank off, it becomes worth repeating and conventional wisdom.
But that doesn't change the fact that it is a lie. It is just a lie that works for us.
From the DSM IV: Mood congruent delusions or hallucinations may accompany severe Major Depressive Disorder.