SCOTTISH justice has been shaken to the roots by the case of Cadder vs HM Advocate, which established the right of suspects to legal advice before questioning.

As a consequence of this ruling by the Supreme Court, the necessity for the alternative safeguard, unique to Scots law, to have corroborating evidence before an accused person can be convicted has been thrown into question.

It is to be expected that the far-reaching recommendations by Lord Carloway for changes to criminal procedure in the wake of the Cadder case would cause deep unease in the legal profession because they overturn centuries-old practice and principle.

However, the Justice Secretary Kenny MacAskill believes that the Carloway report makes a compelling case for removing the requirement for corroboration. The crux of the argument is that the need for corroboration is an impediment to justice rather than a safeguard in a significant number of cases. This is most obvious in rape cases, especially those which hinge on the issue of consent and, because of the inevitable absence of witnesses, are reduced to the word of the victim against the word of the accused.

Shamefully, the majority of rape victims are failed by Scottish justice: only 7% of rapes reported to the police result in conviction. Despite considerable efforts to improve conviction rates, including the establishment of a specialised unit in the Crown Office, Scotland has one of the lowest conviction rates in Europe.

The case for dispensing with corroboration in such cases would seem clear, immediately increasing the number that reach court. But this advantage must be weighed against the risk of innocent men being sent to jail. Ultimately, the absence of corroborating evidence will increase rather than lessen the dilemma facing juries of having to decide whose version of events to believe.

That makes it particularly important to consider two additional safeguards now being proposed by the Scottish Government following the Justice Secretary's acceptance of Lord Carloway's recommendation to abolish the corroboration requirement.

These are to increase the jury majority required to return a verdict and to abolish the not proven verdict. Juries in rape trials are particularly likely to fall back on a not proven verdict, this being the outcome in 21% of rape trials in the past five years. No doubt this reflects a genuine reluctance to brand either the complainer or defendant a liar but is unsatisfactory in terms of justice.

At present, juries in Scotland can convict on a simple majority of eight to seven. There is now a proposal that this should be increased to nine or 10 of the 15 jurors. This would provide a more decisive outcome for any case but would be particularly important if the not proven verdict were abolished, reinforcing a guilty or not guilty verdict.

Corroboration, as a safeguard against wrongful conviction, is a cornerstone of Scottish justice that must not be discarded lightly. In recommending abolition, Lord Carloway called for greater emphasis on quality of evidence, rather than quantity. In all cases, that must be the guiding principle for police and prosecutors.