The Weekend's TV: The Life and Loss of Karen Woo, Sun, ITV1<br/>Louis Theroux: Miami Mega-Jail, Sun, BBC2

Memories that cannot be erased

Technology has done some strange things to grief.

As anyone who's ever had the experience of hearing the voice of a dead loved one on an answering machine will know, it can blur the boundary between presence and absence in a most piercing way. And video can be even more difficult, since being filmed brings out a self-conscious vitality in most of us. It can seem inconceivable that that person, looking directly at you, grinning, is alive on screen and nowhere else. The Life and Loss of Karen Woo, Ursula Macfarlane's very touching film about the killing of a British aid worker, exploited that blurring with great skill. It began with a slightly enigmatic image – a young woman sitting with a pensive, even faintly melancholy expression, which broke at the end into a lovely smile. On the soundtrack you could hear her voice, talking of love and her hopes for the future: "I'd like to be married and have kids and hopefully that will happen," she said. And then you learned that just two weeks before her wedding day, she and her colleagues had been murdered while travelling in a remote area of Afghanistan.

Karen's story was told by the man who was going to marry her, a former British soldier called Paddy Smith who met and fell in love with her in Kabul, where he was working as a security adviser. For this film he'd revisited some of the places where she'd worked, and footage Karen herself had filmed for a planned documentary about her work in Afghanistan effectively allowed Macfarlane to show us what he might be seeing in his mind's eye. The overlaps were often uncanny – locations and local faces unchanged but just one person missing, the person Smith most wanted to see. When he visited a local children's home the image cut between Karen on the playground roundabout, laughing with one of the children, to Smith staring desolately at the same piece of equipment, slowly turning with no one on it.

Such contrasts would have been moving enough whatever she'd been like, but the video footage meant that we didn't have to rely only on the memories of those who loved her to get a sense of her character. You'd expect them to praise her as unique and irreplaceable. But it was less predictable to find that her personality worked on you directly, partly because of her charismatic smile, but also because of a life shaped by a remarkable lack of fear. Woo left home and school at 16 to become a dancer, and the choreographer Richard Alston testified to the fact that she'd been good enough to shine as a performer. But having brought off that large gamble, Woo took another one, going back into education to train as a doctor. And when she'd successfully achieved that, she threw the dice again, giving up a good job in Britain to pursue what for her was far more meaningful work in Afghanistan.

She addressed the risks she was taking with a poignant simplicity. "We plan for the worst and hope for the best," she said, before setting off for a remote area of Afghanistan on a medical mission. Most touching of all, there was footage of her end of one of the last calls she'd made to Smith, telling him that she missed him: "We'll have to go and do lots of camping in the wilderness together," she said. "I love you... don't worry." When she failed to text him a day or two later, he knew that something had gone terribly wrong. MacFarlane left the last words to Woo herself, cutting between her smiling vivacity and Smith, driving at night in Kabul: "Anyone who you see contend with unimaginable adversity, hope is probably what sustained them," she had said, "so what is the point of living without it? Hope is enormously powerful."

There wasn't a lot of hope around in Louis Theroux: Miami Mega-Jail, in which Louis visited a hellish remand centre in Florida: "One of the most violent in the Miami jail system." What he discovered was a system in which violence had been institutionalised, with guards tacitly accepting that any new arrival in one of the big shared cells would either have to deal out a beating or take one. "Ain't no telling what's going to happen once we close that door," said a warder, who was about to lock up a palpably terrified boy in glasses, in on a charge of attempted murder. In fact, there was plenty of telling, mostly by men who seemed to feel they had nothing to lose by a chuckling discussion of their own vicious brutality. "GABOS," explained one terrifying cell kingpin flatly, "... game ain't based on sympathy." Another interviewee – no pushover when it came to fighting his corner – turned up with fresh injuries every time he appeared.

Having made documentaries in US jails before, Theroux can't have been quite as surprised as he made out about the brutality of this one, though I think his shock at "gunning" – public masturbation intended to intimidate and humiliate the guards – was absolutely genuine (particularly when he suddenly became aware that he was being "gunned" himself). What left me baffled was how – in a country as litigious as the United States – no inmate has yet successfully sued the Miami-Dade Corrections Department for the absolutely flagrant breach of their rights under the Eighth Amendment to the Constitution, which prohibits the administration of "cruel and unusual punishment". Perhaps the state's lawyers simply argued that while it might be cruel, there was nothing unusual about it at all.