I used the example of 10 yards because it is not a clear cut case. Somebody running at you aiming a gun ten yards away is not the same as somebody standing still facing away from you holding a knife.
Originally Posted by essence
10 yards away with a knife is still possibly a good shoot, and before long it will likely be a good shoot. There is something pretty well known in legal and self defense/ law enforcement circles as the "Tueller Drill". This is a demonstration, often given to juries, of how someone 21 feet away holding a knife can get to a citizen/cop BEFORE they can draw their carry weapon. The average time for this act is 1.5 seconds. There is currently a lot of discussion around raising the distance from 21 feet out to 30, which would get to your 10 yard example. This increase in distance has been put forth to compensate for the average joe who is carrying concealed, as he will need extra time to get a gun from concealment.
This has been pretty well established and used in court rooms since the mid 80's by the way.
If someone was 10 yards from me threatening me with a knife I would draw my gun and if they moved towards me, I would fire. But, the law in my state is pretty clear on things like this. Some states, not so much.
By the way, this story happened a while ago. The 2 guys knew that her husband had died and they thought he might have some prescription pain pills, that was the reason for the break in.