A lawyer representing a 17-week-old foetus living inside the clinically dead body of its mother says the unborn child's right to life trumps the woman's right to a dignified death.

Conor Dignam made his closing arguments to three Dublin High Court judges who must decide whether Ireland's anti-abortion laws permit the woman's life support machines to be turned off. Their judgement is expected on Friday.

Seven doctors, the woman's father and her partner agreed in testimony yesterday that use of artificial means to sustain the woman's deteriorating body should end because she was declared clinically dead on December 3 and her foetus has no reasonable chance of survival.

But Mr Dignam claimed Ireland's constitutional ban on abortion requires authorities to defend the foetus's right to life if any possibility exists.

Mary O'Toole, a lawyer representing the woman's family, argued that the constitution's anti-abortion amendment is irrelevant to the case.

She noted it commits Ireland to defend the life of the woman and unborn child equally "as far as practicable". But the woman is already dead, and nobody is conspiring to abort a foetus, she argued.

She said the law should permit doctors to take decisions based on feasibility, not futility.

Cormac Corrigan, representing the woman's interests on behalf of the state, argued to keep her on life support. He said it is debatable whether she is legally dead. He said the failing condition of her body since clinical death was declared on December 3 is "as undignified as anyone could ever imagine", but prolonging this could do her no further harm.

One judge, Justice Caroline Costello, intervened to question why the court should agree to sustain the woman in such an appalling state. Mr Corrigan conceded that if it wished to impose "minimum indignity", the court should order that life support ends.

The woman, in her late 20s, has two young children. She suffered catastrophic brain trauma after falling in a hospital bathroom on November 29.