Texas Health and Safety Code Sec. 822.041 

"Dangerous dog" means a dog that:

(A) makes an unprovoked attack on a person that causes bodily injury and occurs in a place other than an enclosure in which the dog was being kept and that was reasonably certain to prevent the dog from leaving the enclosure on its own; or

(B) commits unprovoked acts in a place other than an enclosure in which the dog was being kept and that was reasonably certain to prevent the dog from leaving the enclosure on its own and those acts cause a person to reasonably believe that the dog will attack and cause bodily injury to that person.

As required by State law, owners of registered dangerous dogs are ordered to restrain the dog at all times in an enclosure that prevents the animal from escaping or by someone who can restrain it. The Animal Control Authority will inspect the enclosure and must approve it prior to the owner being allowed to keep the dog. Owners must also purchase $100,000 of liability insurance that specifies: coverage for damages resulting from an attack by the dangerous dog causing bodily injury to a person. Registered dangerous dogs must wear large tags stating they are dangerous as well as green colors at all times. The address and description of the dangerous dog will be publicized. If these animals attack again, they could be put to sleep and the owner charged with a crime.

Sec. 6-39. - Aggressive dogs; levels defined.

Classification of a dog as aggressive shall be based upon specific behaviors exhibited by the dog. For purposes of this chapter, behaviors establishing various levels of aggressive dogs are the following:

• (1) Level 1 behavior is established if a dog, while unrestrained, causes physical injury to any domestic animal or livestock.
   
• (2) Level 2 behavior is established if:
   
  • (a)  A dog, while unrestrained, kills or causes the death of any domestic animal or livestock, or
     
  • (b)  Seriously injured another animal to an extent that an attending veterinarian has presented an affidavit to the animal care services manager stating that the injured animal's life was seriously endangered or taken by the dog, or that the dog caused a significant permanent impairment of the injured animal's basic bodily functions or mobility; provided, however, that when the incident occurred, the injured animal was not in violation of a provision of this chapter relating to the confinement or physical control of animals in the city.
     
• (3) Notwithstanding subsections (1) and (2), the director shall have discretionary authority to refrain from classifying a dog as aggressive, even if the dog has engaged in the behaviors specified in subsections (1) and (2) if the director determines that the behavior was the result of the victim abusing or tormenting the dog or was directed towards a trespasser or other similar mitigating or extenuating circumstances.