Richard Goldberg of the law school at Aberdeen University told The Scotsman he believes prosecutors wanted to make sure that Peter Manuel was executed. Manuel, convicted of seven murders and suspected of eight more killings, was hanged in 1958 at Barlinnie Prison in Glasgow.

Goldberg wants files on the case to be opened. Many of the documents were sealed for 75 years after Manuel's execution.

"When you read the files you see the pressure from the Scottish Home Department," he said. "They look at this issue of his psychopathic personality and they say 'We don't think he's a psychopath, but even if he is a psychopath he's a very marginal psychopath', so there is a pressure on people at the time to get him hanged."

Goldberg has a family interest in the case, since his father, a consultant at Western Infirmary in Glasgow, witnessed an examination of Manuel. Goldberg says that Manuel may have suffered from temporal lobe epilepsy.