Lawyers for Janet Leach, a 42-year-old mother-of-five, took her case to the Court of Appeal on Thursday.

Fred West's confessions contained horrific details of his crimes

Mrs Leach, from Cheltenham, says she suffered post traumatic stress disorder after being nominated as the "appropriate adult" to sit in on West's interviews with Gloucestershire police in the spring of 1994.

Roderick Denyer QC, for Mrs Leach, said she attended 40 interviews over many months and listened to "the most harrowing and horrifying details" of West's crimes.

She became crucial to the investigation and West, 53, refused to talk to the police when she was briefly replaced by another volunteer.

West hanged himself in Winson Green jail in Birmingham on New Year's Day 1995 while awaiting trial on 12 counts of murder.

'Not offered counselling'

Mr Denyer said Mrs Leach was not offered counselling by the police, although it was offered to police officers and the defence solicitor involved in the case.

Mrs Leach, who is now studying to be a social worker, suffered a stroke in November 1995 when she gave evidence at the trial of West's wife Rosemary, who was found guilty of murder and given 10 life sentences.

The trial was halted for several days after Mrs Leach lost the power of speech. She later returned and concluded her testimony with a doctor standing beside her.

In November 1997 Judge Batterbury, sitting at Bristol County Court, threw out her claim for compensation after ruling it would not have been "fair, just or reasonable" to say the police owed her a duty of care.

Rosemary West ... Janet Leach suffered a stroke as she gave evidence against her

Mr Denyer asked three appeal judges to overturn that decision and said police ought to have known there was a danger that having to spend "hours and hours with one of the most notorious mass murderers of the 20th century" gave rise to a risk of psychological injury.

He said Mrs Leach had previously worked for a voluntary organisation working with the homeless and only had experience acting as an "appropriate adult" for mentally disordered youths.

Mr Denyer said she went with West to 25 Cromwell Street, Gloucester, where the couple's victims had been tortured, killed, dismembered and buried.

She was also taken to a field where the remains of one of the victims had been buried.

Mr Denyer said: "The police offered counselling to their own officers and didn't offer it to her. To impose a duty of care in this case is not unreasonable."

'Appointed to advise West'

Simon Freeland, representing the Chief Constable of Gloucestershire, said the force's code of practice required that a person suspected of having a mental disorder could only be interviewed by police if an "appropriate adult" was present to protect their interests.

He said Mrs Leach had been appointed to advise and assist West and not the police.

Mr Freeland said there was no contractual agreement with the police and she was not paid by the force.

He said the police were not in a position to override the legitimate choice of West or his lawyers that she should be the appropriate adult in the case.

The case continues.