Convicted murderer Jerry Gilligan, 72, was convicted of torturing and kidnapping his spouse and stepson Monday, after jurors heard how he also sexually abused the boy.

They were forced to watch a stomach-churning clip of the mother and son having sex with each other, and being forced to perform sex acts on Gilligan.

Gilligan, of Kingman in Arizona, was found guilty of 10 of the 18 charges he faced over the September 2016 incident. It began when his wife, then 39, found him molesting the boy in a backyard shed.

The abuser then bound the woman with rope, chains and duct tape, before battering both with a Taser, knife and wooden rod.

Gilligan killed his stepdad Walter Bopp in Tucson, Arizona, in 1980 and tortured his wife and son within months of being released from jail for that murder.

He also shaved all his victims’ hair off, and poured battery acid into his wife’s eyes. His victims were taken to hospital three days after their ordeal began, with the woman raising the alarm and telling police what had happened to her.

Gilligan’s defense attorney Sandra Carr unsuccessfully tried to claim his victims were lying by asking why the boy had not sustained any physical injuries.

She asked why neither the woman nor her son had used any of the computers or phones in Gilligan’s apartment to call for help.

And Carr also tried unsuccessfully to paint the victim as a gold-digger who had taken advantage of an elderly man for his money.

Gilligan, who is wheelchair-bound due to ill-health, was convicted of kidnapping, torture and sexual contact with a minor, the Mohave Daily News reported.

He will be sentenced at Mohave County Superior Court on December 5, with Judge Billy Sipe warning that he is likely to be jailed for life.