When she was five, Hannah Jones was diagnosed with Leukaemia. Although successfully treated, the drugs weakened her heart and by the time she was twelve it was clear that without a transplant she would die. She declined the offer. Faced with a major operation of uncertain outcome, the prospect of a lifetime on medication, and the likelihood that she would need another transplant in ten years she said she would rather die peacefully at home. This was a young woman, after all, who had endured a great deal of medicine in her short and uneasy life. Tuesday’s documentary Hannah, the girl who said no to a heart followed her for the best part of a year as she lived, and very nearly died, with the consequences of her decision.

Her story first came to public attention in 2008.  A locum doctor, unfamiliar with her case, contacted the local child protection team. Herefordshire PCT started legal proceedings to force a transplant and her family were threatened with her removal. The case did not make it to court. A child protection officer interviewed her. She was competent to make the decision and her family, however reluctantly, supported her. As her mother said, what was she to do, drag her to hospital and force needles into her?

The case is harrowing but, legally and ethically, it is not unique. Chiefly it turns on the question of competence. Broadly speaking where a child possesses sufficient understanding of the consequences of the decision, she can refuse treatment, even where the treatment is thought to be in her clinical interests. Although a court can overrule a child’s refusal of life-sustaining treatment, where the child is competent, and the decision is a considered one, supported by both parents, a court would be unlikely to intervene.

But it is one thing to speak of competence in the abstract, as of a legal get out of jail quick card, quite another to speak of it in relation to a twelve year old girl on the lip of the grave. If there was one thing the documentary succeeded in, it was putting some warm flesh on that abstraction.

As the months of 2009 slid by, so Hannah’s heart deteriorated. The film set her in the familiar rhythms and rituals of a young girl’s life: mornings in the pink Disneyland of her bedroom; a birthday party, Hannah draped in a satin birthdaygirl sash; a rare half-day at school; a few tentative fair rides on holiday in Cornwall. But she was obviously failing. Pale, unsteady, easily exhausted, she picked her way through the days, frequently spending long tracts of time in bed. Ultrasounds showed that her heart was giving out. Her life was running down.

The dilemma behind Hannah’s case is an extreme form of one familiar to every parent. We want our children to grow into independent decision-makers, but we also want to buffer them from harm. For most of us the choice, thankfully, is not a tragic one. We widen the scope of our child’s freedom as her grasp of the world strengthens until one day her life is, as far as anyone’s can be, her own. These decisions are personal. They change from family to family, child to child. Hannah’s parents gave her that freedom very early on. And that is the source of the controversy. At one point Hannah describes pleading with her father for advice about what she should do. And that is the one point in this tender documentary where I misgave, the one point where I thought I could not have held back. Make the choice, I felt like screaming, make the choice to live. Her father declined to guide her.

In the end, life was the choice she made. As death rolled ever closer she changed her mind. And she was lucky. Still strong enough for an operation, a suitable heart was found. The operation was a success. But how would I have felt if she had stood by her earlier decision to let herself die? Even thinking about the question drives home the realisation that while law may be clear the dilemma itself does not cease to tear.

Julian Sheather is ethics manager, BMA. The views he expresses in his blog posts are entirely his own.