The half-sister of two teenagers severely beaten at a church in upstate New York, leaving one dead and the other hospitalized, is due to appear in court on Wednesday on assault charges.

Sarah Ferguson, 33, is accused of participating in a group attack on her 17-year-old brother, Christopher Leonard, during a counseling session last week at the Word of Life Church in Chadwicks, New York, about 50 miles east of Syracuse.

Leonard, who was recently released from a hospital where he was treated for blunt force injuries throughout his body, is expected to testify against Ferguson in New Hartford Town Court on Wednesday.

RELATED: New York teen dies after hours-long beating at church

Ferguson is charged with assault in the second degree, along with three fellow parishioners, and is being held at Oneida County Jail in lieu of $50,000 bail.

The beatings of Christopher and his 19-year-old brother, Lucas, began late on Oct. 11 in the church's "sanctuary room" and lasted more than 10 hours, police said.

Police have said the counseling session was intended to force the teenagers to confess to their sins and apologize. The attack also might have been prompted by rumors the brothers intended to leave the church, police said.

Lucas Leonard died from injuries inflicted during the beatings, in which an electrical extension cord was used, police said. His parents, Bruce Leonard, 65, and Deborah Leonard, 59, have been charged with first-degree manslaughter in his death. They are being held at Oneida County Correctional Facility in lieu of $100,000 bail.

RELATED: Man commits lewd act at Cambridge church altar: Police

Oneida County District Attorney Scott McNamara said last week that he was seeking a grand jury indictment of the Leonards.

Parishioners 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 and are scheduled to appear in court on Dec. 15.