After months of debate between the Scottish Government, the Crown Office and women's campaigners on one side and the legal profession on the other, the first step towards abolishing the corroboration rule in criminal trials has been taken.

The fact that the vote at Holyrood was so close reflects the gravity of the decision, although the opposition parties were also clearly out to make life hard for the SNP (after all, not so long ago abolishing the corroboration rule was in the Labour manifesto).

The change to this ancient rule - or outdated rule as its critics call it - will face further parliamentary scrutiny and a group chaired by the former High Court judge Lord Bonomy is also considering what safeguards will be needed. Kenny MacAskill, the Justice Secretary, has promised the bill will not become law until parliament has considered the judge's report.

But, as was pointed out in yesterday's debate, handling the reform in this way has put the cart before the horse or, in the words of Graeme Pearson, Labour's Justice spokesman, it asks members to write a blank cheque with the promise they will receive the goods later. What the Government's position amounts to is: "this reform may be flawed, but vote for it and we'll fix it later" which is far from ideal. Waiting until Lord Bonomy reported would have been preferable.

Now that waiting for the review is no longer possible, it is more important than ever consideration is given to concerns about the reform. The bill contains good measures - a higher tariff for knife crime, for example, and better pre-trial negotiation - but the worries about the reform will not disappear.

The most compelling argument in favour of the reform has always been that abolishing the need for evidence from two sources would improve the conviction rate for rape. According to the Crown Office, more than 150 cases could not proceed over the last two years because of corroboration.

Mr MacAskill has also pointed out no other country in the civilised world requires corroboration, although he must also know some of those countries do not have a higher conviction rate for rape than Scotland. There has also been persistent concern that dropping corroboration could have the opposite effect. In other words, if the police are no longer forced to find corroborative evidence, is that likely to weaken a case, leading to even less chance of conviction?

In the end, Lord Bonomy may be able to suggest measures that could safeguard against such a risk, although it should be remembered that any case will still have to pass the usual test of beyond reasonable doubt and that is an important safeguard in itself. Whatever happens, a balance between the interests of victims and protecting against the risk of wrongful conviction should be uppermost in the minds of those who vote on whether to change the law. The corroboration rule must not be discarded lightly.