This intentional taking of a life must be vetoed by the House of Lords

The Appeal Court has ruled in favour of murder. The unhappy and intolerable decision to order the killing of the five-week-old conjoined twin known only as Mary is in the worst tradition of English utilitarianism, which exercises a considerable hold over our judges. In the calculus of utility, the choice is between one child surviving and both dying. This seems like a simple, if uncomfortable, decision, and it follows a mechanistic logic that steeled Lord Justices Ward, Brooke and Walker against the counter-arguments.

The Appeal Court has ruled in favour of murder. The unhappy and intolerable decision to order the killing of the five-week-old conjoined twin known only as Mary is in the worst tradition of English utilitarianism, which exercises a considerable hold over our judges. In the calculus of utility, the choice is between one child surviving and both dying. This seems like a simple, if uncomfortable, decision, and it follows a mechanistic logic that steeled Lord Justices Ward, Brooke and Walker against the counter-arguments.

But the court's decision contravenes a prior principle not just of English law but of universal civilised values, namely that murder is wrong.

Until now, of course, such universal values have not been codified in British law. That will change next month, when the universal human rights laid down in the European Convention come into effect in Britain under the Human Rights Act. The first of those rights, under Article 2, reads: "Everyone's right to life shall be protected by law. No one shall be deprived of his life intentionally, save in the execution of a sentence of a court following his conviction of a crime."

Despite all the attempts by doctors and judges to use language diminishing Mary's claim to be a person, this article must apply to her. One of the less pleasant features of this case has been the descriptions of Mary as having a "primitive" brain, as "living off" her stronger sister, and as "draining" Jodie of life, as if she were in some way culpable.

The fact that Mary is going to die anyway cannot possibly give anyone else the right to decide that her few months of life are not worth living, or that she would choose, were she capable of so doing, to sacrifice her life to save her sister's.

There is a secondary, more pragmatic, reason for thinking that the Appeal Court has reached the wrong verdict. That is that the twins are not independent beads on the abacus of life, to be added or subtracted. They are babies, born into a family, to parents who have to care for them, bring them up and take responsibility for them. Their parents have rights - rights which the courts should be most reluctant to abrogate - in deciding issues as deeply personal and tragic as this one.

The judges should be commended on their openness in sharing much of their agonised thought processes with the public, making several statements in court about how they had lost sleep over the case, and even accepting that they were being asked to "save Jodie by murdering Mary", as Lord Justice Ward put it. Unsurprisingly, however, they did not ask themselves whether they had the right to decide the matter in the first place.

It is also a minor consolation that the circumstances of this case are so extraordinary that the precedent it sets is limited. But it is the hard cases which test the law at the edges, bringing definition to the grey areas, and subjecting otherwise abstract principles to the stress-testing of real people in real, heart-breaking situations. The right to life is one such principle, so widely accepted in everyday life that it can be surprisingly overlooked in extreme and unusual cases.

Permission has already been given for this case to go to the House of Lords. The Lords must reverse the decision, thus bringing English law into line with the un-written law of fundamental human rights.