That link puts the reader in the North Carolina Eve Carson murder. That said, a fourteen year old who thinks he may end up a serial killer must have some mental problems he's trying to control. The first "insanity" case, was when the NY Representative who later was Civil War General Sickles, shot and killed the Washington, D.C. District Attorney, the son of Francis Scott Key (wrote the words to the Star Spangled Banner) for his wife's supposed infidelity, when the D.A. walked by and waved a hankie at the house. There was a woman who used to see General Sickles, (famous also for donating his amputated leg to the national medical museum) on the train in Croton, NY. She searched for any writings that his "wife" and he were actually married and found no mention. She was called "Swamp Angel" and the rifled West Point Foundry Parrott gun that fired incendiary shells on the civilians of Charleston, South Carolina and also exploded, in Trenton, NJ was nicknamed for her. It was also a gang of wharf thieves in the port of New York.
So he was acquitted an adult and later general, but a 14 year old might not what, have lived long enough to "experience" momentary insanity?