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PC §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.