WE live in a cynical age. And, in post-Cilla Black, there are few genuine surprises in television.

But BBC Three – of all places – delivered a verdict that was an almighty wallop in Monday’s Life And Death Row.

The three-part documentary series takes on the mighty task of weighing up the scales of justice involved in the death penalty (with a handy ethics code to capital punishment on the BBC’s website). An in-house production by the Beeb, the first two episodes have been the most powerful television in a year, putting all courtroom dramas and cop shows in the shade by taking an unflinching close-up of the people involved.

And it’s the youngest in these confusing, heartbreaking stories who are hardest to take your eyes off. This week’s episode (now on iPlayer, along with the chilling Execution episode) offered a hauntingly dreamlike, lingering look at a Georgia courtroom following the trial of 26-year-old Guy Heinze Jr. As this moon-faced, docile dude stands in the dock, accused of bludgeoning his father and seven other members of his family to death with a rifle butt in their New Hope trailerpark home in 2009, the drama takes on a nightmarish quality.

Five of the 12 jurors are interviewed about their thought processes throughout the trial and the compassion – or otherwise –- they feel towards Heinze in what feels like minute-by minute, shudder-by-shudder analysis. “I was confused probably the majority of the time,” says one wide-eyed juror, aged 22, as a large sign looms in the background, reminding them they need to feel total certainty, without even a speck of reasonable doubt, to judge “murder”. In spite of the documentary series’ resolutely impartial stance (we hear from both sides of the debate, including the impassioned, conflicting story of rape and attempted murder victim Nikki in episode one) you can’t help but feel more than a reasonable slice of doubt about the process.

There are few documentaries so weighed in favour of the truth and the views of the people in the eye of this particular storm. The story is paced in chronological order, and you get all sides, including the horrible hysteria of the US television news and opinion coverage of the mass murder. We hear the motivations of the prosecution and the defence and we sit in the dock with them. Heinze’s distraught 911 call, saying he’d just come home to find his family massacred, echoes around the courtroom.

Examining the injuries and cause of death of each and every dead member of the family took two solid days in court and you wonder how anyone could endure it. But that’s the jurors’ duty: not to mention the relatives’ trying to clear Heinze’s name and save his life. Heinze claims he was in a deserted park nearby smoking crack and marijuana for a few hours before returning to horror and then being arrested as the only suspect. It’s hard to imagine a more horrifying experience, and you almost end up hoping he’d committed the murder to avoid the alternative ordeal he’s ended up tangled in.

Meanwhile, the prosecution maintain Heinze systematically pummeled eight other adults to death inside a mobile home, one by one, on his own. Cut to Heinze’s little brother Tyler; a sweet, articulate youth who has accompanied his grandma Jean to the courtroom for the verdict.

“I’ve been strong up to now, for grandma,” he says. “But I might go crazy if my brother’s not cleared and freed. If it doesn’t happen...” He trails off, unable to cope with the possibility he’ll lose a brother, as well as all his family.

His reaction – and Jean’s – to the final verdict will stay with me for a long, long time.

The series concludes on Monday on BBC Three at 9pm.