IOWA CITY, Iowa (AP) -

An Iowa man who beat a puppy to death with a baseball bat didn't commit animal torture, an appeals court ruled Wednesday, in a decision denounced by one animal rights group.

Prosecutors failed to show that Zachary Meerdink, 31, acted with "depraved intent" when he killed the 7-month-old Boston terrier outside his girlfriend's home in Davenport in 2011, the Iowa Court of Appeals ruled in a 2-1 decision.

The court vacated Meerdink's conviction for animal torture, an aggravated misdemeanor, and the two-year prison sentence he received. He was ordered acquitted of the charge.

Chief Judge Larry Eisenhauer said that proving someone intended to kill wasn't enough to support an animal torture conviction. Instead, prosecutors must prove the defendant acted with "depraved" or "sadistic" intent under the law.

That standard wasn't met because no one witnessed Meerdink killing the dog, it was unclear how many times the dog was struck before dying and Meerdink did not appear to be happy or eager before and after the killing, he wrote. What's more, Meerdink killed the dog after it demonstrated aggressive behavior that was getting worse, including biting a 9-year-old child, he added in a ruling joined by Judge Nancy Tabor.

The founder of a Des Moines-based nonprofit that is pushing for tougher sentences in animal cruelty cases called the decision shocking.

"The decision by the court is inconceivable and breaks the logic barrier," said Lin Sorenson, founder of St. Francis Foundation for Pets. "Beating an innocent dog to death with a baseball bat meets the level of sadistic intent necessary in the Iowa Code to constitute animal torture."

Meerdink was living with his girlfriend and her sons in 2011, and she bought him the puppy while he recovered from shoulder surgeries. The girlfriend, Jamie Holladay, testified that the puppy had accidents in the home because of a weak stomach, often jumped on people, had bitten her and her three children, and wasn't responding to coaching.

Holladay said that she was running an errand when Meerdink called to ask where the Lysol spray was because the dog had an accident by the door. When she returned, Meerdink walked out of the house with the dog under his arm. He came back minutes later carrying a baseball bat and said the animal was dead.

Holladay panicked, ordering Meerdink to leave and calling police. An officer found the dead dog in tall grass behind her home, suffering from a head injury near a pool of blood.

Judge Cheryl Traum found Meerdink guilty after a bench trial, saying the animal's death was enough to justify the torture charge. The act of hitting a dog in the head with a bat shows a depraved intent because it was obvious severe physical pain would result, she ruled.

Dissenting Judge Anuradha Vaitheswaran agreed, saying she would have upheld Meerdink's conviction and sentence. Police photos shows the dog lying on its side with a bloodied eye and mouth and significant bruising in the head region, she noted.

She rejected claims that Meerdink acted only after the puppy bit a child, saying there was no evidence of a biting incident on the day of the killing and the law doesn't allow for a justification defense.

"A reasonable fact-finder would not have had to engage in any speculation to find that Meerdink took a baseball bat to the head of the puppy in response to the puppy's accident," she wrote. "A reasonable fact-finder could have found this conduct to be an extreme response to an ordinary and foreseeable occurrence."

The dissent went on.

"A reasonable fact-finder could have found depravity based on the dog's age, the fact that the act was precipitated by nothing more than the puppy's weak stomach, the inference that Meerdink spent some time searching for a blunt instrument with which to kill the dog, the uncontested fact that Meerdink inflicted 'severe physical pain,' and the fact that the animal was a family pet."

Prosecutors and defense attorneys had no immediate comment. Meerdink's prison term had been ordered to run consecutively with one from a previous drug conviction, and he was released on paroled in April.