Also, Crusty is correct. Horn's defense wasn't just that he was protecting his neighbor's property, but that supposedly one of the criminals charged at him when he confronted them. What set his case apart from others was that there is no "duty to retreat" law in Texas, therefore the fact that he initiated the personal conflict with the thieves was irrelevant.
Texas Penal Code Title 2 Chapter 9.
http://www.statutes.legis.state.tx.us/docs/PE/htm/PE.9.htmSec. 9.43. PROTECTION OF THIRD PERSON'S PROPERTY. A person is
justified in using force or
deadly force against another to protect land or tangible, movable property of a third person if, under the circumstances as he reasonably believes them to be, the actor would be justified under Section 9.41 or 9.42 in using force or deadly force to protect his own land or property and:
(1) the actor reasonably believes the unlawful interference constitutes attempted or consummated theft of or criminal mischief to the tangible, movable property; or
(2) the actor reasonably believes that:
(A) the third person has requested his protection of the land or property;
(B) he has a legal duty to protect the third person's land or property; or
(C) the third person whose land or property he uses force or deadly force to protect is the actor's spouse, parent, or child, resides with the actor, or is under the actor's care.