The point here was that he wasn't defending his home and family. He could easily not have opened fire, but chose to instead, killing a 16-year-old. You would kill a defenceless person because they tried to take your stuff? They tried to take your posessions, so you have to take their life? A human life is a human life, no matter how it is used. Avoid death wherever possible, and maybe the world would be a better place. The burglar may not be innocent, but they do not forfeit their right to life.
IIRC, John Locke said that every human being has a right to "life, liberty, and property." Frederic Bastiat said not too long after that you have "a natural right to defend your person, your liberty, and your property." The kid was on the man's premises, violating his rights to property. Now, unless you can prove that he was coerced into being there by his adult partner, then he just as much forfeited his right to life by violating someone else's right to property.
Of course, that's just what the defense would argue. I in no way condone what he did, as it was excessive force and unnecessary, given that the two were already fleeing when he brought out the shotgun.
Oh and before you get all sentimental about Tony Martin lets remember that this man is a supporter of the neo-nazi BNP party, shot the burglars with an illegal shotgun and was himself arrested in 2004 for theft.
Oh wow.
You know, even a half-assed defense lawyer would've put in a motion to exclude all of that nonsense in a heartbeat based on the fact that it serves no legitimate purpose other than to inflame emotion and violate a man's right to free association. The only thing prosecution can do with any of that is use the theft charge to establish a pattern of behavior. So tell me, if I were a member of the Klan, does that somehow make me more guilty in a murder situation than someone who wasn't?
So I don't know exactly what you're doing by bringing this up, but please, stop the demonizing. Poor character or not, the man deserves every single right to defend himself and his property, and be fairly represented in court without that tosh being thrown in as an accusation.