In line with Mary's comments, I strongly recommend that martial arts students research their own local laws regarding self defense. Some states establish a duty to retreat while others don't. There is no simple explanation that cuts across all jurisdictions. You simply have to know and apply the law in your jurisdiction in a situation like this, or you are in grave danger of running afoul of the law even if you feel your actions are reasonable.
I agree. Here in the "wild west," there is no duty to retreat. Perhaps more importantly, the legal doctrine called "defense of habitation" would have provided fairly broad protection to the Dowdy's, and likely would affect a prosecutor's decision whether to go forward with criminal charges.
Here, "defense of habitation" provides even deadly force may be used to prevent the commission of "a felony" within a defendant's home. The felony being prevented is not
limited to felonies that pose an immanent risk of death or great bodily harm to the defendant (or another).
A New Mexico jury in a criminal case brought against someone under the facts related likely would receive the following jury instruction (with blanks filled in based on the facts of the case as provided by the use notes):
14-5170. Justifiable homicide; defense of habitation.1
Evidence has been presented that the defendant killed __________________ (name of victim) while attempting to prevent a __________________2 in the defendant's __________________3.
A killing in defense of __________________3 is justified if:
1. The __________________3 was being used as the defendant's dwelling; and
2. It appeared to the defendant that the commission of __________________2 was immediately at hand and that it was necessary to kill the intruder to prevent the commission of __________________2; and
3. A reasonable person in the same circumstances as the defendant would have acted as the defendant did.
The burden is on the state to prove beyond a reasonable doubt that the defendant did not kill in defense of __________________3. If you have a reasonable doubt as to whether the defendant killed in defense of __________________3, you must find the defendant not guilty.
1. If this instruction is given, add to the essential elements instruction for the offense charged, "The defendant did not kill in defense of __________________3".
2. Describe the felony being committed or attempted.
3. Identify the place where the killing occurred.
So, local laws do differ in important was. Still, to say that a jury might acquit doesn't mean that it will. If
the state disproves that a "reasonable person in the same circumstances as the defendant would have acted as the defendant," the jury should convict.