By Aman Ali

NEW YORK (Reuters) - A New York jury cleared a woman who shot dead her retired police officer husband of murder on Thursday in a case that had been seen as a test of the battered-woman defense.

Barbara Sheehan, 50, was acquitted of second-degree murder after three days of deliberations by the jury in state Supreme Court in Queens but was found guilty of a lesser charge of gun possession.

Sheehan's lawyers successfully argued that she fired only after her husband threatened to kill her, and Sheehan and her grown children had testified about the violent household ruled by Raymond Sheehan, 49, a former New York City Police sergeant.

Both the prosecution and defense said the beatings and bruises came to an end on February 18, 2008, when Sheehan shot her husband 11 times in their Queens home.

Legal experts said the case was a test of the battered-woman defense, in which the history of abuse is explored to explain a woman's mental state at the time she is accused of committing a crime.

Sheehan, wearing a purple scarf around her neck as she often does for domestic violence awareness, declined to speak to reporters as she left the courthouse.

Queens District Attorney Richard Brown called the case "terribly sad and tragic," but warned in a statement after the verdict that victims of domestic abuse should seek help through the legal and social services systems, not through violence.

"Six million American women are beaten each year by their husbands or boyfriends," he said. "Think of where we would be if only a fraction of abused women took the law into their own hands."

Key to the battered-woman defense is the issue of self defense. New York state law justifies the use of lethal force in response to an immediate threat to life. Under the battered-woman defense, lethal force can sometimes be justified even if the threat may not appear immediate.

Jurors came to their decision after reporting to Judge Barry Kron on Wednesday that they were deadlocked.

Court documents said the shooting happened after Sheehan refused to go on vacation with her husband. She testified she was scared because he had threatened to kill her if she didn't go.

Prosecutors said Sheehan shot her husband 11 times using two guns the former police officer had at home. Her husband was in the bathroom shaving before Sheehan shot him.

According to court documents, Sheehan told police the night of the incident: "I shot him! I shot him! I think he's dead. He's in the bathroom."

The defense said he had grabbed a gun he kept in the bathroom and pointed it at her head, and she shot him in self defense.

The gun possession charge, based on Sheehan's use of her husband's weapons, carries a possible sentence of 3-1/2 to 15 years in prison. Sentencing was not set but would likely take place in early November.

(Editing by Ellen Wulfhorst and Cynthia Johnston)