(Missouri New Service) Missouri's Stand Your Ground law has been cited a number of times since the recent shooting of a Missouri teen by a homeowner whose house he went to by mistake. But one expert said the statute is not what authorizes a person to use lethal force when a "legitimate" threat occurs at their home or property.

Ari Freilich, state policy director for the Giffords Law Center to Prevent Gun Violence, pointed out Stand Your Ground laws apply in public spaces, and the Castle Doctrine covers private property.

He said what the two have in common is lowering the legal requirement to avoid using lethal force when possible, by stepping away, or otherwise de-escalating the situation.

"Generally speaking, you cannot use lethal force unless it was objectively reasonable for you to believe that it was necessary to use that amount of force to prevent death or serious bodily harm, or really serious crimes from occurring," Freilich explained.

Freilich noted both the Castle Doctrine and Stand Your Ground laws fall under the umbrella of homicide laws. He added although every state has variations, the legal system has important protections, independent of the two, in the form of self-defense and justifiable homicide laws.

Freilich stressed although the Castle Doctrine does not require someone to step away or attempt to de-escalate a threat when at home, it has major restrictions.

"That does not authorize someone to use lethal force when there is no reason to believe that someone is unlawfully entering the home," Freilich emphasized. "And also, when there is really no objectively reasonable indicator that the person was a threat to life or safety."

And although de-escalating has historically been the expectation in public spaces, Freilich acknowledged people's understanding of this seems to be changing.

"Stand your ground laws have altered and distorted that and told people they have some vague affirmative right in public spaces -- wherever they might lawfully be present -- to stand their ground and not withdraw, not de-escalate in that way," Freilich said.

Freilich co-authored a study with the Southern Poverty Law Center which concluded Stand Your Ground laws should be repealed, stating, "They encourage a trigger-happy culture of anxious vigilantism that cheapens the value of human life. And they deepen vast and harmful disparities in our legal system."