The Christian parents of an American teenager teenager who was beaten to death during a church counselling session have been sentenced to prison.

Bruce and Deborah Leonard, aged 66 and 60, who are members of Word of Life in New Hartford, 250 miles north of New York, were sentenced to 10 and five years respectively.

Their beating of their sons, Lucas, 19 and Christopher, 17, lasted for more than 12 hours. 

In an attempt to forced the boys to confess sins and seek forgiveness, the boys received multiple fist blows to their abdomen, genitals, back and thighs from their parents. A black extension cord was also used to whip them.

At an earlier hearing, Christopher said the beating took place because his brother had expressed his wish to leave the church. 

When Lucas stopped breathing, he was taken hospital where he died. Police then went to the church to investigate and discovered Christopher, also seriously injured. 

Nine people have been convicted, with the boys' older half-sister, Sarah Ferguson, 33, sentenced to between 25 years and life.

A lawyer told the court that Deborah Leonard had felt helpless to stop the beating. She had pleaded guilty last month to first- and second-degree assault charges in exchange for her testimony against her husband and seven others, including their pastor, Tiffanie Irwin.

The boys' parents were sentenced at Oneida County Court on Monday as part of a plea deal, according to CBS News. Bruce Leonard had his sentence reduced by a judge from 16 years after pleading that he was a "changed man" who had been subjected to cult-like mind control by the church. 

"There's no way I would ever condone that. No way I would ever go along with it," he said, according to the Rome Sentinel.

Bruce Leonard at an earlier hearing rejected a plea deal that would have sent him to prison for at least 18 years.