Originally, English common law was based on the sanctity of human life, and really the only person authorized to take a life was the King.
In fact, if someone came after you, you were supposed to retreat to the “wall behind your back” before fighting back with force. That was called the duty to retreat. The King was the one who was there to protect the people.
The one exception to that was the “castle doctrine,” which originates in the early 1600s. This was the doctrine that you did not have to retreat from an attack if you were in your home, because as the old adage says, a man’s house is his castle.