George Reimus built a massive bootlegging empire during prohibition. His wife was by his side during his ascent to becoming a major kingpin and he provided her with anything she ever wanted.
Reimus gets sent to prison for a short 2 year prison term. He left her in charge of his entire empire while he was incarcerated. She was his soulmate and he trusted her completely, without hesitation.
His wife starts sleeping with a new man. Within 6 months, she sold all of her husband's assets, stole all his money, and filed for divorce.
Upon his release, George was driving to his divorce hearing when he spotted his wife in another car. He forced her car off the road, then shot and killed her. He immediately turned himself in and admitted to the murder.
At his trial, he pleaded temporary insanity and won. He said this afterwards:
It was a duty I owed society. She who dances down the primrose path must die on the primrose path. I'm happy, this is the first piece of mind I've had in years - George Reimus
The problem with this defense is the fact that it's simply not real.
"Temporary insanity" is a legal term but isn't at all a real psychological phenomenon. In fact, in reality, there is no sanity or insanity or even a "real you." There are just moment to moment brain states which are a result of biological, chemical, physiological, environmental, etc factors.
That guy wasn't "temporarily insane." His behaviour was the end result of a specific set of factors which were in play the moment he saw his wife; the reason he had never acted that way before was simply because he has never been in that situation before. Just like when an otherwise "friendly dog" attacks someone. They aren't insane in that moment; they were acting on circumstances that hadn't been in play prior to that moment.
