Tex. R. Civ. P. 38

(a) When Defendant May Bring in Third Party. At any time after commencement of the

action a defending party, as a third- party plaintiff, may cause a citation and petition to be

served upon a person not a party to the action who is or may be liable to him or to the

plaintiff for all or part of the plaintiff's claim against him. The third-party plaintiff need not

obtain leave to make the service if he files the third-party petition not later than thirty (30)

days after he serves his original answer. Otherwise, he must obtain leave on motion upon

notice to all parties to the action. The person served, hereinafter called the third-party

defendant, shall make his defenses to the third-party plaintiff's claim under the rules

applicable to the defendant, and his counterclaims against the third- party plainti ff and

cross-claims against other third-party defendants as provided in Rule 97. The third- party

defendant may assert against the plaintiff any defenses which the third- party plaintiff has

to the plaintiff's claim. The third-party defendant may also assert any claim against the

plaintiff arising out of the transaction or occurrence that is the subject matter of the

plaintiff's claim against the third-party plaintiff. The plaintiff may assert any claim against

the third-party defendant arising out of the tra nsaction or occurrence that is the subject

matter of the plaintiff's claim against the third-party plaintiff, and the third-party defendant

thereupon shall assert his defenses and his counterclaims and cross-claims. Any party may

move to strike the third-party claim, or for its severance or separate trial. A third-party

defendant may proceed under this rule against any person not a party to the action who is

or who may be liable to him or to the third-party plaintiff for all or part of the claim made

in the action against the third-party defendant.

(b) When Plaintiff May Bring in Third Party. When a counterclaim is asserted against a

plaintiff, he may cause a third party to be brought in under circumstances which under this

rule would entitle a defendant to do so.

(c) This rule shall not be applied, in tort cases, so as to permit the joinder of a liability or

indemnity insurance company, unless such company is by statute or contract liable to the

person injured or damaged.

(d) This rule shall not be applied so as to violate any venue statute, as venue would exist absent

this rule.