How many people actually get away with a major crime if its considered a Cromer of passion.?

If a woman was to kill a man who has abused her physically and mentally for many years and the woman one day finally snaps and somehow kills the man, one of the biggest defence that the accused would be able to present would be the condition of battered woman's syndrome. It would only be a small mitigating circumstance unless the accused also somehow proves that she did not have the intent to kill the man. No, people actually do not simply get away with cases involving a persons life. More commonly, people, in a sense, kind of get away with murder if they proved that they weren't resposible for their actions due to insanity.