In a criminal court, a case must be proved beyond reasonable doubt, but the jury is still out on whether the Scottish Government's case for scrapping the corroboration rule has passed that level of test.

Almost the entire legal profession and judiciary in Scotland is lined up against the move and in the preliminary findings of his recent review into the proposal, Lord Bonomy said wide-ranging safeguards would have to be introduced to prevent miscarriages of justice if the change to the law went ahead and the corroboration rule was scrapped.

Scrapping the rule, which requires evidence from two separate sources to secure a conviction, was originally suggested by the senior judge Lord Carloway in his review of the criminal law four years ago. Supporters of the move said they believed it could lead to more prosecutions for rape and other sexual offences, which often fail because of a lack of corroboration. The Crown Office, which supports the change, says hundreds of cases do not proceed because there is no corroborating evidence.

However, the criticism of any move to drop corroboration has been fierce. Not only is there a concern that removing the requirement for at least two pieces of evidence could increase the chances of a miscarriage of justice, the Faculty of Advocates has also suggested the Scottish Government's plans could achieve the exact opposite of what is intended and make it harder to secure convictions because cases without corroborating evidence would be more likely to fail in court.

It is not an easy argument to resolve, but it now appears to have become personal as well. In a speech at a legal conference in Edinburgh at the weekend, Lord Carloway suggested that at least some of the hostility from lawyers towards his proposals was motivated by financial self-interest. "Reactionary or excessively defensive forces amongst the legal profession," he said, "can, and often do, behave in a manner obstructive to progressive law reform, especially where there is transparent perceived financial self-interest."

It was pretty direct language but it has now provoked an equally direct response from the Criminal Bar Association, which has suggested that if self-interest really were the motivation, defence lawyers would actually support the end to corroboration on the basis that the reform could lead to more prosecutions and therefore more income for lawyers. Thomas Ross, the association's chairman, says: "Every single defence lawyer I know is against a measure that would increase his or her cash flow."

The suggestion that lawyers might be acting in their own self-interest also adds little of great significance to a debate that will have to be decided by the Scottish Government on the weight of the legal evidence. The most tempting argument in favour of the reform has always been that abolishing corroboration would improve the conviction rate for rape, but the concerns that the reform would achieve more convictions at the expense of fairness to the accused have persisted. Evidence in court would naturally still have to be proved to a jury beyond reasonable doubt even after an end to the corroboration rule, and that would provide some protection, but the reform should not go ahead if it would upset the balance between the interests of victims and protecting against the risk of wrongful conviction.

When Lord Bonomy delivers his final report in the coming weeks, he may be able to suggest measures that could safeguard against such a risk, but whatever happens the corroboration rule should not be discarded lightly and it will probably have to be retained in some form in some cases. The Scottish Government may argue that no other country requires corroboration in the same way that Scots Law does, but it is equally true that many of those countries have lower rape conviction rates even than Scotland. Four years after it was first suggested and with the row between lawyers no closer to being resolved, the case for ending corroboration has still not been established. It is for the Scottish Government to prove it now beyond reasonable doubt.