Gary Brown was banned from driving

The ruling has averted fears of chaos within the Scottish courts system.

An estimated 4,000 motorists who have been charged or convicted of drink driving were awaiting the outcome of the case.

Drivers who fail a roadside breath test are taken to a police station where an intoximeter is used to measure the level of alcohol on their breath.

A test case was brought by 49-year-old Gary Brown, of Carrick Place, Tamfourhill, Falkirk.

He was fined £250 at Falkirk Sheriff Court and banned from driving for a year after being convicted of drink driving in January 2000.

Five-day hearing

His legal team claimed that the intoximeter equipment was unreliable.

A sheriff ruled against Brown last November following a five-day hearing at Falkirk Sheriff Court.

The case was then referred to the appeal judges.

During lengthy submissions Neil Murray QC, for Brown, argued that the motorist had suffered a miscarriage of justice.

Complex tests

He said the device was unreliable because it did not always discriminate between alcohol on the breath and that found in the mouth, which might give a higher reading.

However, Edward Targowski QC, for the Crown, said the device was subjected to rigorous and complex tests and met the required standards.

Lord Cameron, sitting with Lord Hamilton and Lord Morison, announced on Friday that they would reject the appeal.

Written reasons will be given later.