Roger Stringer and his son Zac are from Mississippi, in the deep south of the USA. They're from a community where guns and hunting are part of the culture. And growing up, Zac and his brother Justin loved to hunt deer with their dad in the forests around their home.

On a summer's evening in 2011, Roger dropped 15-year-old Zac and 11 year-old Justin home after taking them out for a meal. Twenty minutes later, he got a call from the boys' mother. She was screaming. Then, another call - it was Zac. What he said would change everything.

Zac had loaded a rifle to threaten Justin, just to scare him, he says. But when he went to put it down, he heard a click. The rifle had gone off and struck Justin in the head, who died instantly. Zac swore he hadn’t pulled the trigger, but Roger didn’t believe him. And in Zac’s trial, Roger testified against his own son, saying that guns don’t fire by themselves.

But when Zac went to prison Roger made a discovery that turned their lives upside down.

Warning: this programme descriptions that some listeners may find distressing.

Image: Roger & Zac Stringer

Credit: Ashton McKenzie/Shutterup Photography