If Sheila had not seen a psychiatrist for 18 weeks that is not the fault of the prosecution or the jury.
Sheila had lots of friends the defence could have spoken to. Such as Freddie Emami, who the police interviewed at lenght, Sandra Elston & Dorothy Brencher. She also had a social worker for a period called Barbara Babic. Maybe the defence did question these people & included this evidence to their psychiatrists. The answer still being 'no' Sheila did not have the potential to erupt into such murderous violence.
Yes,,,Freddie,,who was scared sh1tless one night when Sheila had a psychotic episode,,but sadly,what he had to say,didn't reach the ears of the jury.
Don't forget that this wasn't a unanimous decision either. Rather telling,don't you think ?