Both called 911 to report themselves, which does show that they KNEW what they had done was wrong.
That's all it takes to defeat the insanity defense in Texas. Knowing right from wrong, whether or not they were able to control their own actions. Most states have a much more lenient standard of what insanity is than Texas does.
The jury screwed up here.
But the difference between the two cases is that here the murder was brutal. In the Yates case, drowning is not bloody.
My criminal law professor informed me during the first two weeks of class that the best way to get away with murder is to make the bloodiest, most grotesque, murder scene possible. Odds are the jury is going to think, "only a crazy person would do something like that."
My professor was right.