post partum depression is general broken into 3 categories (or so it was last time i checked several years ago). They are:
PP Blues- feeling sad for up to 2 months
pp Depression- deep depression lasting up to a year or more
pp Psychosis- just like it sounds. woman has psychotic symptoms and could do something psycho.
In most of these cases the victim is the baby, but psycho is psycho and who's to say the husband couldn't be the victim.
I'm not condoning this. I don't even think that any type of insanity is a defense for murder.
I imagine here psychosis refers not to going bonkers enough to rampage but a clinical "loss of contact with reality."
A clinical psychotic episode wouldn't turn a person into a psychopath. That said...it still might have been a part of the motive (i.e. delusions).