I know how this storyline goes down -- and again, it's a fantastic example of this series's commitment to having its characters make huge, plausible mistakes, and then live with the life-changing consequences -- but this absolutely seems like an open and shut case of self-defense. Vance is already severely physically injured, to the point where he couldn't reasonably defend himself with his arms or legs. His dad immediately starts hitting him hard enough to draw blood. His dad has him down on the floor in a vulnerable position, with his mother incapacitated and unable to intervene, and is announcing his intention to keep hurting Vance when Vance lashes out. Also, his dad KNOWS Vance has these powers and STILL chooses to attack him.

Not really concurring with the subsequent courtroom logic, is what I'm saying.