Scotland's top law officers were left embarrassed yesterday after a High Court judge criticised them in front of two United Nations observers.

The legal experts were in the public benches of the court in Glasgow to examine the Scottish legal system.

They will report back to UN Secretary General Kofi Annan as to whether the Lockerbie bombing suspects in Libya should face a Scottish court or be tried in another country.

They were in Court Three of Glasgow's #28m showpiece court extension, when a woman first offender admitted a charge of trafficking in cannabis.

Advocate depute Mr Allan Dewar, prosecuting, was asked by Lord McCluskey why it took the Lord Advocate's office so long to bring the case to court and why it was there at all.

College student Miss Lesley Green, 29, admitted to police after her arrest 10 months ago dealing in more than #3000 worth of cannabis from her Glasgow flat, said Mr Dewar.

He said: ''It has probably taken since February to bring to court because of the pressure of business.

''The Crown were not aware until last week that the accused, who was on bail, was offering to plead guilty.''

Lord McCluskey said: ''I am puzzled as to why this young woman, accused of dealing in a modest amount of a Class B drug, should be before the High Court.

''There is no justification for bringing this case to the High Court and it is incomprehensible that it has taken 10 months to bring to court when she freely admitted her guilt to police at the time of her arrest.''

Mr Dewar said the judge's comments would be passed on to Lord Hardie, the Lord Advocate in charge of the Crown Office.

Green, of Armadale Street, Dennistoun, Glasgow, will be sentenced later this month.

She admitted dealing in cannabis from her flat over a one-month period after her plea of not guilty to trafficking in the drug for a year was accepted by the Crown.

The two UN experts, Dr Enoch Dumbutshena, a former Chief Justice of Zimbabwe, and Professor Henry Schermers, a Dutchman and former Justice of the European Court of Human Rights, declined to comment after the case.

They also observed two other court cases before visiting Barlinnie Prison.