Lisa Hopfer, 34, was found guilty Wednesday in St. Charles County Court of misdemeanor assault and trespassing. She is scheduled to be sentenced Sept. 25.
The trial featured X-rays and pictures of the dead dog, and testimony from the woman who claimed to have been hit over the head repeatedly by the animal.
“She's somebody I never want to be in the presence of again,” the victim, Linda Hulsey, told the St. Louis Post-Dispatch. She now lives in Alabama.
The assault occurred June 7 at Husley's home in St. Peters after the Chihuahua she sold to Hopfer died.
Hulsey, 33, said she was hit with the dead puppy at least 30 times.
Hopfer told St. Peters police that after buying the puppy - which she said Hulsey told her was 6 weeks old - a veterinarian said it was only 4 weeks old and needed to be returned to its mother. The dog died before Hopfer could return it.
Police said Hopfer pushed her way inside Hulsey's home and began fighting with Hulsey and pulling her hair.
Outside of the home, Hopfer took the dog out of a plastic bag and started hitting Hulsey over the head with it, police said.
Hulsey went to a hospital for some bruises, but had no serious injuries.
After the incident, she returned the $100 that Hopfer had paid for the dog - one of five puppies born April 27 - and took back the other puppies because she was afraid they might also be ill.
The four surviving pups were in good health and later put up for adoption.
Hopfer testified Wednesday that she never hit Hulsey with the dog, but only yelled at her and held the dog out of the sunroof of her car as she drove away.
Hopfer, who did not have an attorney, held up X-rays of the dead dog and said she had signed statements from two veterinarians saying that the dog didn't appear to have broken bones.
Hopfer now has a new dog, she said, also a Chihuahua.
“She's doing great,” she said.