I do believe the law is not that different (in regard to this scenario) from USA to AUST.
Here, in real laymans terms, you have the right to use lethal force to protect yourself or someone else from serious harm or death AND there is no other option.
If you are able to lock a door to prevent that attack then that is another option. If you are in a position to run away, then that is another option. If all other options have been considered and attempted and there is still no other option, then one may be justified (legally) in using lethal force. Even then the force is not referred to as lethal but as reasonable. For instance if producing a firearm and aiming at someone causes them to drop the weapon or it eliminates the immediate threat, then firing at the person would be excessive. If shooting at someone and hitting them in the leg causes them to drop the weapon and lie on the ground screaming in agony and they are no longer a threat, putting a couple more into them might well be seen as excessive.
If all they were doing was wearing ski masks it would be hard to justify (legally anyway). If that were the case anyone in a burqa would be fair game.
However if they came into a store and the clerk were to draw on them and they continued to approach in a menacing manner, it could well be argued that three aggressive men in that way meant to do harm to the clerk and provided no other options were available to the clerk then reasonable force may include firing at the men.
If I were the first on scene and the clerk told me that three men entered, wearing ski masks, and he/she felt an immediate threat to themselves and that they felt under the circumstances that they had no other option than the course they chose to protect their own lives, then I would do everything in my power to assist them.
Alternatively if I were to attend and find three idiots playing a practical joke lying face down on the ground in little pools of their own urine with a store clerk holding a gun to their head, even if the clerk's actions may border on excessive force, I would most definately explaining in very plain English to the three idiots why it is really stupid to enter a store with a ski mask on unless you plan on robbing it. I did in fact have a young man enter a service station with a brown paper bag over his head and buy something and leave. We worked out who he was (due to excellent Police work
) and attended his house. In no uncertain terms he was given several reasons why that was a really dumb thing to do, including the line where I told him that if I was driving past and saw him do it, he could explain to me why he ws doing it AFTER i took him down at gun point and had him in cuffs.
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