The last reported prosecution for ‘murmuring’ – or slandering – judges under Scottish law seems to have been in 1870 and the offence must now be obsolete.

So there seems little chance of seeing the first minister of Scotland, Alex Salmond, in the dock for his extraordinary personal attack last week on the deputy president of the UK Supreme Court, Lord Hope.

Salmond was being interviewed on the BBC’s Newsnight Scotland programme about a ruling given by the Supreme Court in a murder case nearly a week earlier.

Five judges sat – the usual number – and were unanimous in allowing the appeal.

But that was not the impression Salmond gave viewers.

‘In the most recent case of Nat Fraser,’ he said, ‘one Scottish judge gave an opinion.

'I don’t think it’s sensible, fair or reasonable in any jurisdiction to have a situation where one judge is overruling the opinion of many judges in another court.

‘It’s all very well for people to criticise judges in the Court of Session,’ the first minister continued, ‘but why not criticise a situation which boils down to the potential replacement of Scottish law with Lord Hope’s law?’

Salmond chose his words carefully.

It is true that only one Scottish judge delivered a judgment in the Fraser case.

But three other judges agreed with every word of it. The fifth member of the court, Lord Brown, expressed doubts but did not carry them to the point of dissent.

The first minister knew perfectly well that it was five judges – not one – who had overruled a decision by three judges in the Court of Session, while leaving the Edinburgh court to decide on a retrial.

Salmond also knew that the other Scottish judge, Lord Rodger, had agreed with Hope.

Why didn’t Rodger deliver a judgment of his own?

Four weeks after the hearing, the court announced that Rodger was ‘unwell’ and would be undergoing treatment.

It turned out that he was suffering from a brain tumour that had gone undiagnosed for some time.

What is not clear is whether the tumour was already having an effect on his faculties at the time of the hearing.

But he was certainly in no position to write a judgment afterwards.

What is clear, though, is that Fraser’s original trial was a miscarriage of justice.

The case against him was that he had arranged the murder of his wife, Arlene, who disappeared from their home at Elgin in April 1998.

Fraser was alleged to have put three rings worn by his wife into the bathroom of their house a few days after she was last seen in order to make it look as if she’d simply walked out.

The case was presented to the jury on the assumption that Arlene Fraser was wearing her rings when she left home.

But after the trial it emerged that a police officer had told prosecutors he thought he had seen the rings in the bathroom after the time she had disappeared.

That was confirmed by another officer.

Anyone can see that this information should have been disclosed to the defence before the trial.

But the Court of Session found a way to dismiss Fraser’s appeal.

Under Scottish law, that should have been the end of the matter.

Scotland has never allowed criminal appeals to the House of Lords or its successor, the Supreme Court.

But ever since the Scottish parliament was re-established in 1999, there has been a backdoor route to London.

An appeal could be heard by the Judicial Committee of the Privy Council if it raised what’s called a devolution issue.

As the name suggests, these include disputes between the Scottish parliament and the Westminster parliament over whether a particular power has been devolved to Scotland. But schedule 6 to the Scotland Act 1998 is more widely drafted, covering questions of whether Scottish ministers have acted compatibly with the human rights convention.

Fraser’s lawyers argued that the Crown’s failure to disclose evidence about his wife’s rings undermined his right to a fair trial.

This appeal route may have been unforeseen and unintended but it has worked well enough since 1999; nobody saw any harm in transferring it to the new Supreme Court a decade later.

There wasn’t even much of a fuss when the Supreme Court ruled, in the Cadder case last October, that it was unlawful for suspects to be detained and questioned by the police for up to six hours without the right to have a solicitor present.

The Scottish government simply asked an appeal judge to review the law.

Why, then, is Salmond gunning for the Supreme Court, with a second inquiry now in train?

Why is he talking of scrapping criminal appeals from Scotland?

Why does he think that a court with no full-time Scottish judges would have a better understanding of Scottish law than a court in London which ensures that every appeal from Scotland is heard by at least two Scottish judges?

The answer is that the European court – unlike the Supreme Court – cannot quash decisions by the Scottish judges.

Scotland would still have to bring its law in line with the Human Rights convention if the court were to find it wanting.

But it would do so at a time and in a way of its own choosing.

This all boils down to more power for Scotland – which is just what you would expect a Scottish nationalist to be aiming for.