Willie Cantu had just finished work one day last year and was out walking his Chihuahua when he heard the painful wails of another dog.

Operation Kindness/FILE 2006

Mercy, a pit-bull mix, died shortly after a plasma transfusion at a veterinary clinic where she was receiving treatment for her injuries.

"I hear a yelp, like a really loud bark," Mr. Cantu said Tuesday as he testified on the first day of the animal cruelty trial of Deshawn Brown. "Then I see an engulfed flame going down the street."

Mr. Cantu said he and two other men cornered the burning dog, who became known as Mercy, and while Mr. Cantu used his shirt to smother the flames, the other two men poured beer on the animal.

"I had singed hair all over me, like charcoal and ash," Mr. Cantu testified. "The smell was really intense – singed smell of hair, gasoline and burned skin."

Mercy, who was also stabbed, died 10 days later. Mr. Brown, 22, is charged with animal cruelty and faces up to 10 years in prison. In July, Mr. Brown rejected a plea deal for an eight-year sentence.

His attorney, Dan Wyde, said Tuesday that his client is innocent.

"Not one witness is going to come forward and say they saw Mr. Brown hurt this dog," Mr. Wyde told the jury.

But prosecutor David Alex said Mr. Brown was angry because he was being evicted from his North Dallas apartment, and his dog – whom he named Brandy – wouldn't breed.

"This case is serious, because when a person stares into the face of unconditional love, and in response to that douses their pet with a flammable liquid and ignites it on fire, these are actions of torture; sadistic acts of torture," Mr. Alex told the jury during his opening statement.

In April 2006, said Forrest Pyle, 17, he was hanging out with Mr. Brown at the apartment complex. He grudgingly described seeing Mr. Brown take Mercy behind a trash bin with a knife in hand, hearing the dog yelp, and then watching her scurry into view.

"He came out and threw the knife down," Mr. Pyle said of Mr. Brown. "I never really seen him hurt the dog. I just seen the dog and seen the knife."

After Mr. Cantu and the other men aided the dog, police arrived and allowed Mr. Brown – who showed up on his bike carrying a gasoline can – to keep the dog with the assurance that he'd seek medical attention for her, Mr. Alex said.

The next day, Austin Holt, a resident in the same apartment complex, noticed the dog running outside his patio window. Initially, Mr. Holt said, he did not know what was wrong with the animal.

He attempted to give her water and food but she would not take it. Mr. Holt said he thought she might have mange and was afraid to touch her. So he and a friend took her to Operation Kindness, a no-kill shelter in Carrollton.

In court Tuesday, two veterinarians testified for the prosecution, using grisly photographs to help describe how Mercy was burned over 60 percent of her body and to show her two puncture wounds.

Mr. Wyde, however, contended that the prosecution's case is weak. He said some of the witnesses should not be believed because they were influenced to come forward by reward money. In addition, Mr. Wyde said, other potential suspects were ignored by police.

Sandra Brown, Mr. Brown's mother, would not talk about her son's case Tuesday. But she issued a written statement declaring that he would never torture or kill his own dog. She described how he cared for several pets, including two other dogs, two cats and a snake.

"My son lived in an apartment and would call me and ask if he could bring his dogs over to run around my back yard because they have been in the apartment all day," Ms. Brown said.