An ordinance singling out pit bulls as vicious animals is unconstitutional, the attorney for a pit bull breeder said Thursday in the opening day of a 2nd District Court trial challenging the North Salt Lake ordinance.

The ordinance is being challenged in a suit originally filed by Ralph Greenwood of North Salt Lake, who owned Greenwood Kennels and bred pit bulls. Greenwood died last year, but the suit is being carried on by his daughter, Kate Greenwood.Greenwood attorney David White said the two-year-old law is vague and arbitrary, singling out owners of pit bulls and people who may not even be aware they own a pit bull or a dog that is part pit bull.

And, White said in his opening argument, there are so many physical variations in the breed that a person of average intelligence, including those charged with enforcing the ordinance, may not be able to readily tell if a dog is a pit bull or not.

Kent Christiansen, city attorney for North Salt Lake, told Judge Rodney S. Page the city is charged with protecting the health, welfare, and safety of its residents, and the council decided that certain breeds of dogs constitute a threat.

After extensive research, Christiansen said, the council decided that the breeds listed in the law are dangerous, aggressive, and unpredictable and requirements for their ownership and licensing should be broadened.

The ordinance requires owners of vicious dogs to keep them in a pen or enclosure at least 6 feet high, leash and muzzle them when out of the enclosure, and maintain a $100,000 liability policy for legal protection.

The ordinance was challenged by Ralph Greenwood six months after its approval. Greenwood was editor of a national pit bull magazine and president of the American Dog Breeders Association, a pit bull fanciers organization.

Greenwood died in February 1988 and the suit was delayed but is now being pursued by his daughter, Kate, who assumed her father's jobs as magazine editor and association president.

The North Salt Lake ordinance defines the American pit bull terrier, bull terrier, American staffordshire terrier, staffordshire bull terrier, tosa, and shar-pei as vicious dogs, automatically requiring the enclosure, muzzling, and insurance stipulations before the animals can be licensed.

Much of Thursday's opening session was devoted to testimony from Kate Greenwood on how appearance standards for various breeds of dogs are developed by canine organizations and how individual dogs are judged according to those standards.

The five breeds referred to as pit bulls vary widely in size, shape, color and body conformation, she testified, and some other breeds of dogs, including crossbreeds, also resemble what is commonly considered a pit bull.

She owns two American pit bull terriers, Greenwood testified, but cannot license them in North Salt Lake because she cannot obtain the $100,000 in personal liability insurance the ordinance requires.

But Christiansen, through cross-examination, elicited the testimony that Greenwood Kennel and the American Dog Breeders Association comply with the city's ordinance because they are commercial operations and carry more than the required amount of insurance.

Greenwood acknowledged that pit bulls historically were bred as fighting or bear- and bull-baiting dogs. Individual dogs can be aggressive, she said, but the breed as a whole should not be classified as vicious.