Think there's been a discussion on here before about something similar. It's all about reasonable and excessive force. If you stab a burglar once, from the front, if you are in genuine fear of your life, then that can be deemed reasonable. If you repeatedly stab, that's where it becomes excessive. Also if they are running away and you stab them, or shoot them (a la Tony Martin) then that also can be deemed unnessessary and therefore excessive. I'm all for a persons right to defend there family and homes, and it is the burglars own risk, but I dont think murder equates to burglary and I dont think its every persons right to kill a burglar UNLESS there is a genuine threat of physical harm/ self defence.
And if you're suggesting we should bring back capital punishment for burglary then that's just insane.