|Briefly, English common law transplanted to the American colonies permitted one to stand one's ground in the face of attack, but only in limited circumstances. A person under attack had a duty to retreat from the attack if it could be done so safely. If a retreat could not be accomplished safely, then the person under attack could use deadly force to protect him or herself against death or serious bodily injury. Traditionally, there was one exception to this duty; a person did not have to retreat in his or her own home. It did not matter if he could retreat safely. One's home was one's castle.
As settlers pushed west during the 19th century, the duty to retreat evolved and - well - retreated. The notion of retreat became associated with cowardice and judicial opinions concerning self defense began to be littered with words and phrases such as "true man" and "American man." The notion of retreat became so disfavored that by the early part of the 20th century, no less a justice than Oliver Wendell Holmes, Jr., wrote, "Detached reflection cannot be demanded in the presence of an uplifted knife."
Texas common law reflected these changes and was ultimately codified. Section 9.31(a) of the Penal Code reads thus:
"(a) Except as provided in Subsection (b), a person is justified in using force against another when and to the degree the actor reasonably believes the force is immediately necessary to protect the actor against the other's use or attempted use of unlawful force. The actor's belief that the force was immediately necessary as described by this subsection is presumed to be reasonable if the actor:
(1) knew or had reason to believe that the person against whom the force was used:
(A) unlawfully and with force entered, or was attempting to enter unlawfully and with force, the actor's occupied habitation, vehicle, or place of business or employment;
(B) unlawfully and with force removed, or was attempting to remove unlawfully and with force, the actor from the actor's habitation, vehicle, or place of business or employment; or
(C) was committing or attempting to commit aggravated kidnapping, murder, sexual assault, aggravated sexual assault, robbery, or aggravated robbery;
(2) did not provoke the person against whom the force was used; and
(3) was not otherwise engaged in criminal activity, other than a Class C misdemeanor that is a violation of a law or ordinance regulating traffic at the time the force was used."
Section 9.31(e) explicitly eliminates the requirement to retreat, and Section 9.31(f) states that under this section, neither judge nor jury may consider whether the person retreated, while determining criminal culpability.
Section 9.31(d) then goes on to limit the use of deadly force to an ostensibly discrete set of circumstances also found in Subchapter C of the Penal Code. Those alleged limits, however, are simply the situations found in Section 9.31(a), but where the person reasonably believes that not just any force will do - deadly force must be employed (Section 9.32); instances of protecting a third person (Section 9.33); and preserving another's life in an emergency (Section 9.34). (Section 9.34, despite its seeming inherent contradictions, does not permit the use of deadly force to prevent another from committing suicide. Yet, it does allow the use of deadly force to preserve the life of another in an emergency; which begs the question, against whom is that deadly force to be used?)
The Texas law departs radically from the traditional notion of self defense. In the age-old tension between dignity of the person and dignity of life, it seems to err on the side of dignity of the person. Where the traditional notion of self-defense gave a person the right to use deadly force once he had retreated "to the wall," and where the wall was often confined to one's home, Texas expands the scope of where a person may use deadly force: to the home, to the car, to the person's own business, and even to the person's place of employment, as well as to anywhere where they may be to prevent various violent crimes.
Notably, the law gives an enormous amount of discretion to the actor who seeks to use the force in any of these situations. The standard employed is reasonable belief. Therefore, if a person uses deadly force, and she is entirely mistaken about the actions or intentions of the person against whom she uses the force, but she were reasonable in her belief (and mistake), there is no culpability. Further, the statute and case law also permits a person to use deadly force and not just do so while retreating or merely standing his ground; he can actually pursue the person against whom he seeks to use the force if doing so is consistent with the rest of the law, or even depart from the retreat in order to retrieve a weapon to fight back.
The statute also presents other issues. If a person is engaging in criminal activity, he cannot avail himself of the protections of the statute. In a sense, this is like a trial before a trial. Before a person has been convicted of engaging in criminal activity - even in her own home - she must surrender any protections she may have had to defend herself under this law. Section 9.34 is perhaps the least intuitive and least interpreted section of the Texas law. For instance, a person may use deadly force to preserve the life of another in an emergency. Interestingly, case law has established that this does not apply to unborn children or fetuses. Still, it is unclear which lives are to be protected under this section or against whom the force is to be used. However, the section does seem to provide some clarity as it states that force, but not deadly force, may be used to prevent someone from committing suicide. Which, given the law's aversion to linguistic surplusage, would seem to prevent an absurd result of killing someone to prevent his suicide, but removes an attempted suicide from the definition of emergencies.
* Thanks to Richard Maxwell Brown, No Duty to Retreat: Violence and Values in American History and Society (1991) for backgrounder on the evolution of law on the American frontier.