It would be difficult to plead insanity in this case.
The shooters attorney (assigned to him by the State of Florida) said in court that the shooter was fully aware of what he had done.
The act itself was premeditated ... as soon as he was caught, after leaving the campus and visiting a nearby Walmart and Subway,
the shooter admitted to the police that he indeed had been the shooter.
The shooter even wore a gas mask and set off the fire alarm to get more people out of their classrooms to shoot them.
He will get the death penalty and it will take forever to serve justice and of course this act will breed even more shooters to imitate this one.