It was a crime that shocked the nation and could have come straight from the pages of an Agatha Christie novel – a dead Black Country nurse and a doctor tried but dramatically acquitted of murder.

Now, 50 years on, the mystery of who really killed New Cross Hospital nurse Martha Giles has taken a new twist with the news her family has been denied access to the case files from the time.

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The mother-of-five, from Carlton Avenue, in Wednesfield, was found dead on the bowling green of the Wolverhampton hospital on February 12, 1959, after failing to turn up for a night shift the previous evening.

She had been battered with a rock and stabbed in the heart and lung but, despite the atrocity being given national media coverage, the 45-year-old’s murderer was never brought to justice.

A doctor at the hospital was charged and sent to trial at Staffordshire Assizes in July of that year where a not guilty verdict was returned by the jury and he was discharged. No other person was sought by police in connection with the killing.

Mrs Giles’ great-niece, crime writer Pauline Rowson, had hoped to mark the 50th anniversary of the death with some solid leads but today told how a Freedom of Information request to the National Archives, where documents relating to the case are held, was turned down.

In rejecting her application, the archives’ FOI officer said there remained a possibility, “however remote”, that the case could be opened for reinvestigation at some point in the future. The 52-year-old, whose novels have been published in the UK, US and Poland, now fears the information will be withheld until 2030 at the earliest.

“It’s very disappointing,” she said. “I’ve got newspaper coverage of the murder and spoken to some of the officers involved at the time but this is like hitting a brick wall.

“I won’t give up though and I am planning to try an appeal as well as contacting my MP.”

Mrs Rowson, from Hayling Island in Hampshire, thinks the murder may have subconsciously inspired her crime-writing career. She said: “It was something that was talked about a lot when I was a child.