The teenager whose brother was beaten to death in their Word of Life Church in upstate New York testified against his half-sister in court yesterday.

Christopher Leonard's brother Lucas was killed and Christopher himself was treated for injuries to most of his body in the attack, which involved their own parents. 

The assault, which began late on October 11 in the church's "sanctuary room" and lasted more than 10 hours, was initiated because Lucas Leonard wanted to leave the congregation, District Attorney Scott McNamara said.

The teenager's testimony came during a hearing for his half-sister Sarah Ferguson, 33, in New Hartford Town Court. He spoke quietly in court and kept his head down while answering questions from attorneys.

Christopher was giving his first public account of the event that led to his hospitalisation and his brother's death. Six people have been arrested, including the brother's parents and half-sister, Sarah Ferguson.

He was beaten until he was put in another room with earplugs and earmuffs to hide him from the sound of what was then unfolding. "It hurt everywhere", he said.

When he was brought back to the sanctuary where the beating had taken place, he found his brother collapsed on the floor.

The spiritual "counselling session" was a response to Lucas' desire to leave the Word of Life Christian Church, which is a small and highly controlling congregation in upstate New York.

Leonard testified that after an eight-hour Sunday service on October 11, his family were asked to stay behind by the Pastor Tiffanie Irwin to "talk about what we had done. Lucas and I."

He estimated that the beating he received lasted over six hours, during which he was pummelled with fists and whipped with a four foot, folded electrical cord. He suffered injuries to his torso and genitals.

When he found his brother, he and a church leader tried to revive him.

Leonard was barred from riding in the family car to the hospital with his brother. He was taken by a member of the congregation but did not go inside. Instead, they drove him back to the church, where they made a bed for him on the second floor. He went to sleep, although it hurt to breathe and he was vomiting repeatedly.

Police have said his parents refused to tell them where he was and a former congregation member finally told them over the phone after they had searched for hours.

McNamara said: "I can't imagine the stress he was under to go into the courtroom... to testify against his sister."

The teenagers' parents, Bruce Leonard, 65, and Deborah Leonard, 59, have been charged with first-degree manslaughter in the death of Lucas Leonard. They are being held at Oneida County Correctional Facility in lieu of $100,000 bail.

Ferguson is charged with assault in the second degree in the beating of Christopher. She is being held at Oneida County Jail in lieu of $50,000 bail.

Congregation members Joseph Irwin, 26, Linda Morey, 54, and David Morey, 26, are also charged with second-degree assault in connection with Christopher Leonard's beating. They have been released after posting $50,000 bonds.

Irwin, Ferguson, both Moreys and the teenagers' father, Bruce Leonard, are said to have been the primary assailants,

The defendants are scheduled to appear again in court on December 15.

The Word of Life Christian Church is a reclusive community in New Hartford, a town of 22,000 people. Once a lively and joy-filled house of worship, former members have described its decline into a place of fear and intimidation.

Additional reporting by Reuters.