In the United States of America, stand-your-ground law states that a person may justifiably use force in self-defense when there is reasonable belief of an unlawful threat, without an obligation to retreat first. The concept sometimes exists in statutory law and sometimes through common law precedents. One key distinction is whether the concept only applies to defending a home or vehicle, or whether it applies to all lawfully occupied locations.
Under these legal concepts, a person is justified in using deadly force in certain situations and the "stand your ground" law would be a defense or immunity to criminal charges and civil suit. The difference between immunity and a defense is that an immunity bars suit, charges, detention and arrest. A defense, such as an affirmative defense, permits a plaintiff or the state to seek civil damages or a criminal conviction but may offer mitigating circumstances that justifies the accused's conduct.
More than half of the states in the United States have adopted the Castle doctrine, stating that a person has no duty to retreat when their home is attacked. Some states go a step further, removing the duty of retreat from other locations. "Stand Your Ground", "Line In The Sand" or "No Duty To Retreat" laws thus state that a person has no duty or other requirement to abandon a place in which he has a right to be, or to give up ground to an assailant. Under such laws, there is no duty to retreat from anywhere the defender may legally be. Other restrictions may still exist; such as when in public, a person must be carrying firearms in a legal manner, whether concealed or openly.
"Stand your ground" governs U.S. federal case law in which right of self-defense is asserted against a charge of criminal homicide. The Supreme Court of the United States ruled in Beard v. U.S. (158 U.S. 550 (1895)) that a man who was "on his premises" when he came under attack and "...did not provoke the assault, and had at the time reasonable grounds to believe, and in good faith believed, that the deceased intended to take his life, or do him great bodily harm...was not obliged to retreat, nor to consider whether he could safely retreat, but was entitled to stand his ground."
Justice Oliver Wendell Holmes, Jr. declared in Brown v. United States (1921) (256 U.S. 335, 343 (16 May 1921)), a case that upheld the "no duty to retreat" maxim, that "detached reflection cannot be demanded in the presence of an uplifted knife".
Effect on crime rates 
The law's effect on crime rates is disputed between supporters and critics of the law. The third edition of More Guns, Less Crime (University of Chicago Press, 2010) by John Lott says that states adopting “Stand Your Ground”/"Castle doctrine" laws reduced murder rates by 9 percent and overall violent crime by 11 percent, and that occurs even after accounting for a range of other factors such as national crime trends, law enforcement variables (arrest, execution, and imprisonment rates), income and poverty measures (poverty and unemployment rates, per capita real income, as well as income maintenance, retirement, and unemployment payments), demographic changes (broken down by race, gender and age), and the national average changes in crime rates from year-to-year and average differences across states (the fixed year and state effects).
A study by Texas A&M economics professors found that the adoption of stand-your-ground laws caused a statistically significant increase in the raw homicide rate, and had only a very small positive effect on deterrence of crime. The authors of the study were unable to determine what percentage of the increase was justifiable homicide, due to the reporting of homicide to the FBI often lacking notation whether the homicide was justifiable or not.
Another analysis of stand-your-ground laws by economists at Georgia State, using monthly data from the U.S. Vital Statistics, found a significant increase in homicide and injury among whites, especially white males. They also analyzed data from the Health Care Utilization Project, which revealed significantly increased rates of emergency room visits and hospital discharges related to gun injuries in states which enacted these laws.
In a 2007 National District Attorneys Association symposium, numerous concerns were voiced that the law could increase crime. This included criminals using the law as a defense for their crimes, more people carrying guns, and that people would not feel safe if they felt that anyone could use deadly force in a conflict. The report also noted that the misinterpretation of clues could result in use of deadly force when there was, in fact, no danger. The report specifically notes that racial and ethnic minorities could be at greater risk because of negative stereotypes.
Florida state representative Dennis Baxley, an author of the law, notes that crime rates in Florida dropped significantly between 2005, when the law was passed, and 2012. However, crime rates had been declining in Florida as well as nationally since at least 2000. Representative Baxley told Politifact Florida that he does not believe his law is the main reason for the drop in crime rates in Florida, but may be one of several reasons.
United States 
Many states have some form of Castle Doctrine or Stand Your Ground law. Alabama, Alaska, Arizona, California, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Massachusetts , Michigan, Mississippi, Missouri, Montana, New Hampshire, North Carolina, North Dakota, Ohio, Oregon, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, West Virginia, Wisconsin and Wyoming have adopted Castle Doctrine statutes, and other states (Iowa, Virginia, and Washington) have considered "Stand Your Ground" laws of their own.
Some of the states that have passed or are considering "stand your ground" laws already implement "stand your ground" principles in their case law. Indiana and Georgia, among other states, already had "stand your ground" case law and passed "stand your ground" statutes due to possible concerns of the case law being replaced by "duty to retreat" in later court rulings. Other states, including Washington and Virginia, have "stand your ground" in their case law but have not adopted statutes; West Virginia had a long tradition of "stand your ground" in its case law before codifying it as a statute in 2008. These states did not have civil immunity for self-defense in their previous self-defense statutes.
Controversy in Florida 
Stand-your-ground laws are frequently criticized and called "shoot first" laws by critics, including the Brady Campaign to Prevent Gun Violence. In Florida, the law has resulted in self-defense claims tripling. The law's critics argue that Florida's law makes it very difficult to prosecute cases against people who shoot others and then claim self-defense. The shooter can argue that they felt threatened, and in most cases, the only witness who could have argued otherwise is the victim who was shot and killed. Before passage of the law, Miami police chief John F. Timoney called the law unnecessary and dangerous in that "[w]hether it's trick-or-treaters or kids playing in the yard of someone who doesn't want them there or some drunk guy stumbling into the wrong house, you're encouraging people to possibly use deadly physical force where it shouldn't be used."
In Florida, a task force examining the law has concluded that the law is "confusing." Those testifying to the task force include Buddy Jacobs, a lawyer representing the Florida Prosecuting Attorney's Association. Jacobs recommended the law's repeal, feeling that modifying the law would not fix its problems. Florida governor Rick Scott plans his own investigation into the law.
The Trayvon Martin case brought a large degree of criticism to the law. Legal experts are split as to whether charges will be dropped under Florida's stand-your-ground law before the case even goes to trial, as the extant Florida law allows the shooter, George Zimmerman, to argue that the charges should be dropped before trial even begins. Legal experts are also split as to whether Zimmerman's actions will be viewed as self-defense, should the case go to trial.
- Florida Statutes Title XLVI Chapter 776
- "Kopel DB: "The Self-Defense Cases," 2000". Davekopel.com. Retrieved 2012-03-23.
- "''Beard v. United States'', 158 U.S. 550 (1895)". Supreme.justia.com. Retrieved 2012-03-23.
- Brown v. United States, 256 U.S. 335, 343 (1921)
- More Guns, Less Crime: Understanding Crime and Gun Control Laws (University of Chicago Press, third edition, 2010).
- "Does Strengthening Self-Defense Law Deter Crime or Escalate Violence? Evidence from Castle Doctrine". Retrieved 19 September 2012.
- "Study Says ‘Stand Your Ground’ Laws Increase Homicides - Law Blog - WSJ". Retrieved 19 September 2012.
- McClellan, Chandler; Erdal Tekin (June 2012). "Stand Your Ground Laws, Homicides, and Injuries". Bulletin on Aging and Health. NBER Working Paper No. 18187.
- "Half true:Crime rates in Florida have dropped since 'stand your ground,' says Dennis Baxley". Politifact. March 23, 2012. Retrieved March 24, 2012.
- "Crime rates in Florida have dropped since 'stand your ground,' says Dennis Baxley". Politifact Florida. Tampa Bay Times and The Miama Herald. Retrieved 16 January 2013.
- Ala. Code 13A-3-23(b): "A person who is justified under subsection (a) in using physical force, including deadly physical force, and who is not engaged in an unlawful activity and is in any place where he or she has the right to be has no duty to retreat and has the right to stand his ground."
- Martosko, David (April 1, 2012) "'Stand your ground' laws not just GOP policy, records show" The Daily Caller. Retrieved 2012-04-03.
- Penal Code §§ 197, 198.5, Legislative Counsel, State of California, retrieved April 3, 2012
- "CALCRIM No. 505. Justifiable Homicide". CaliforniaJuryInstructions.Net. January 2006. Retrieved April 3, 2012.
- "Iowa Code Section 704.1".
- "11-8-8". Rilin.state.ri.us. Retrieved 2012-01-11.
- "Gov. Perry Signs Law Allowing Texans to Protect Themselves", Office of Governor Rick Perry Press Release, March 27, 2007
- 76-2-405 "Force in defense of habitation". Utah criminal Code.
- "HF2215 An Act relating to the justifiable use of reasonable force and providing a remedy.".
- "HB 48 Castle doctrine; self-defense and defense of others.". Virginia's Legislative Information System.
- "Fortifying The Right To Self-Defense". National rifle Association. February 26, 2006.
- "Castle Doctrine: Protecting Our Right to Self-Defense". National Rifle Association. (map showing states which have enacted a Castle Doctrine law)
- Willing, Richard (March 20, 2006). "States allow deadly self-defense". USA Today. Retrieved April 4, 2006.
- See State v. Cain, 20 W.Va. 679 (1882); State v. Laura, 93 W.Va. 250, 116 S.E. 251 (1923); State v. McMillion, 104 W.Va. 1, 138 S.E. 732 (1927); State v. Preece, 116 W.Va. 176, 179 S.E. 524 (1935); State v. Bowyer, 143 W.Va. 302, 101 S.E.2d 243 (1957); State v. Green, 157 W.Va. 1031, 206 S.E.2d 923 (1974); State v. Kirtley, 162 W.Va. 249, 252 S.E.2d 374 (1978); State v. W.J.B., 166 W.Va. 602, 276 S.E.2d 550 (1981)
- "Florida 'Stand Your Ground' law could complicate Trayvon Martin teen shooting case". MSNBC. March 20, 2012. Retrieved March 21, 2012.
- "Deaths Nearly Triple Since 'Stand Your Ground' Enacted". CBS Miami. 2011-03-20. Retrieved 2012-03-23.
- Goodnough, Abby. "Florida Expands Right to Use Deadly Force in Self-Defense". The New York Times. nytimes.com. Retrieved March 23, 2012.
- Goodman, Howard. "NRA’s Behind-the-Scenes Campaign Encouraged ‘Stand Your Ground’ Adoption". Florida Center for Investigative Reporting. fcir.org. Retrieved March 23, 2012.
- "Trayvon Martin case: Florida task force told 'stand your ground' law confusing". TheGrio. April 6, 2012. Retrieved April 6, 2012.