For example, the theory of plate tectonics is a scientific theory. There is ample evidence, which is indisputable, that the surface of the Earth is divided into solid plates that have moved over geological timescales.
Scientific theory is much different than legal theory but those who casually study personal protection often confuse the two. “Legal theory refers to the principle under which a litigant proceeds, or on which a litigant bases its claims or defenses in a case.” Legal theory is much closer to being a hypothesis, in the scientific sense. In some ways, legal theories are not even hypotheses but are, in fact, merely speculation by an attorney.
We ignore this distinction at our peril. A recent court decision in Pennsylvania provides good examples of why. Among those with a casual knowledge of personal protection concepts, the phrase ‘disparity of force’ is parroted as an almost ironclad defense if a much larger person has been shot. However, ‘disparity of force’ is merely a legal theory that one’s defense attorney can raise at trial. While the defense might be bolstered in this effort by expert witnesses, the shooter cannot take it for granted this theory will have any effect on the outcome.
Similarly, the concept of ‘shoot him to the ground’ is often blathered on about. This idea is rooted in the notion that ‘if the first shot was justified, the rest won’t matter.’ As can be seen in the Pennsylvania case, courts may find this idea unconvincing.
The Kimball case in Maine gives another example of how these two often regurgitated legal theories failed to sway either the jury or the court. “Kimball’s attorneys argue Cole made a mistake by not instructing the jury that it could find that Kimball had been adequately provoked by Kelley, who was 6-foot-4 and 285 pounds, after being repeatedly struck as he retreated away from Kelley.” The Maine Supreme Judicial Court found this argument unconvincing and rejected it. Merrill Kimball, 74 years old, will spend the rest of his life in prison, an unpleasant prospect. The fact he fired three shots rather than just one was raised at trial by the judge.
There are other legal theories I periodically hear that, while they sound good, similarly cannot be counted on to prevail in a courtroom. We need to be cautious about using potential legal theories an attorney could raise in our defense when formulating the doctrine we will use for our decision-making.
The law is not logical and does not necessarily ‘make sense’ to the uneducated. We are best served by being knowledgeable, rather than speculating, about what it is or assuming what we think it should be. The one assumption we can make is that nearly everything we read on the Internet about the law is wrong.
For those who carry weapons of any kind, including personal weapons (hands, feet, etc. as the FBI defines them), obtaining some real legal training is well worthwhile. Law Of Self Defense, Massad Ayoob Group, the Armed Citizens’ Legal Defense Network, and other organizations provide information, not speculation, about what we can and cannot do in our defense and the defense of our loved ones. The cost is about equal to one hour of a criminal defense attorney’s time; that’s a good tradeoff.
Note: I am not a lawyer and by no means am I giving legal advice. I am merely pointing out fallacies in thinking that I often observe.
Fair disclaimer: I have taken training from Law Of Self Defense, Massad Ayoob Group, and am a local affiliate trainer for the Armed Citizen Legal Defense Network.
tacticalprofessor 
There are no ABSOLUTE arguments at trial–if such arguments were at hand, you wouldn’t BE at trial. If you’re at trial, it’s because the prosecution believes he has a narrative of guilt that can defeat your defense narrative of innocence. The jury will ultimately weigh those narratives and arrive at a verdict.
One should always attempt to stay out of the Justice System. It is easy to find cases where the use of deadly force is thought to be justified, but the verdict is otherwise. One should attempt to retreat, even in the home. Any shooting will be costly and should be avoided by verbal instructions to the miscreant, but never with a warning shot. If a firearm is used, it must be used properly to STOP the attacker, not kill the attacker. The attacker may be killed, but the intent should be to STOP the attack. If possible, all shots should be made during a retreat or from a point where there is not escape from the attacker. Know that once shots are fired, there will be great costs to the attacked victims in the justice system. Assuming that the Criminal Justice System hurdle is cleared, there is the Civil Justice System that may rear its ugly head. There will be costs to the shooting victim no matter what the attack outcome is. Use deadly force carefully. Think ahead about circumstances where one might have to use deadly force in general terms. There are an infinite number of scenarios that may happen, but having a general plan will help when under the pressure of an attack to make the better decision and take the defendable approach to the situation.
Make certain that you have a good defense attorney. He WILL be required. Research what response should be conveyed to the law enforcement authorities. Know that one should always consult an attorney before providing information to law enforcement personnel. What you say WILL be used against you. They will tell you that right before you are arrested. Never think that just because you think a shooting is justified, that the Criminal Justice System will treat you like a victim. Tables turn quickly, especially when there is a death involved. Be aware, be cautious, be alert, and ALWAYS avoid using your firearm IF you can. If a firearm must be used, use it wisely and know that tough times are ahead.