VITAL evidence on the mysterious death of SNP activist and campaigner Willie McRae – including the gun that killed him – is inexplicably missing from police files, the Sunday Herald can reveal.

Police have also formally admitted for the first time that the weapon was not swept for fingerprints, while other key forensic evidence was not gathered from the scene.

McRae, a Glasgow lawyer and leading light within the SNP, died on April 7, 1985 after appearing to crash his car on a lonely Highland road. However, a single gunshot wound to his head was later discovered in hospital.

Rumours of involvement by the security services have persisted for three decades, due to McRae's politics and campaigning – yet the official stance has always been that the wound was self-inflicted.

Now it can be revealed the .22 Smith & Wesson revolver found at the scene, said to be illegally owned by McRae, has disappeared with no administrative record as to why it was discarded, where it ended up, or when it vanished.

Other items recovered from the area and from McRae's person whilst he was in hospital – including files which, for many years, were said to be linked to his anti-nuclear campaigning – are also no longer in the possession of Police Scotland.

And vital forensic evidence to support the assertion that McRae committed suicide does not exist.

Police have admitted for the first time in correspondence that the gun was not swept for fingerprints and McRae's car and clothes, which may also have contained vital evidence such as fingerprints, gunpowder residue and blood spatter, were not subject to any forensic analysis.

Much of the suicide theory has been hinged on McRae's history of depression and previous drink-driving convictions. A partially-consumed, half-bottle of Famous Grouse whisky – not one of McRae's usual brands – was found in his crashed car on the banks of Loch Loyne, by Invergarry.

However, it can be revealed that McRae's body had point zero blood alcohol level at the time of post-mortem.

John Finnie, the Green Party candidate for the Highlands and Islands, claimed that long-standing interest in the case had always “been fuelled by a dearth of some fundamental information”.

“The public will be rightly astonished that the weapon allegedly used in this case was neither fingerprinted nor subject to basic forensic examination,” he added.

In 2007, it was first revealed that two statements were missing from the police files on the case. It is now understood that these statements were from former officers of the Northern Constabulary. And that both statements are missing from the Crown Office files on the case.

The Crown Office had evidence that the statements existed in 1985, but no explanation has been offered as to why no moves were made to secure them, or why they were ignored.

It was not until the Crown Office was alerted to the discrepancy in early 2015 – nearly 30 years after McRae’s death – that it made efforts to directly contact the two officers involved.

While a new statement was eventually secured from one of the officers, the second had since died.

Finnie, a former police officer, added: “Perhaps most worrying has been the Crown Office’s inability to appreciate that the number of statements they had in respect of this death excluded two statements taken from police officers.

“And until such time as satisfactory explanations are given, if indeed they can be, then the understandable concern that exists about Mr McRae’s untimely death will continue.”

A Crown Office and Procurator Fiscal Service (COPFS) spokesperson said: “Crown Counsel are satisfied with the extensive investigations into the death of William McRae and the case is now closed.”

Mark MacNicol, spokesman for the Justice for Willie McRae campaign, said 13,000 people had now backed a petition and crowdfunding campaign calling for a fresh inquiry into the SNP activist’s death.

He added: “After 30 years of Chinese whispers we want to finally be able to separate fact from fiction.

“Regardless of the Crown Office position our campaign is about getting to the truth."

Police Scotland said a report had been sent to the procurator fiscal following an investigation into McRae’s death on April 6, 1985, and further reviews carried out in 2010/11 did not raise any new matters.

“Any further information or evidence reported to Police Scotland on any case will be always be considered," it added.