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Crown cuts drink drive margin of error as new limits come in

5 December 2014

Drivers just slightly over the new drink driving limits, which come into force in Scotland today, could find themselves being prosecuted after the Crown announced a restriction of its previous policy regarding marginal cases.

Under new guidelines from the Lord Advocate, Frank Mulholland, where there is sufficient and reliable evidence, and where it is in the public interest to do so, the Crown will prosecute drink drive cases that contravene the law.

With the previous breath alcohol limit of 35 microgrammes in 100ml of breath, guidelines issued in 1983 stated that no proceedings would be instituted on the basis of a breath/alcohol reading less than 40 microgrammes.

Drivers who have a reading not substantially over the limit will still have the right to have their breath sample replaced with a blood or urine specimen. Under the previous limit, this applied where the breath reading was below 50; with the new limit of 22 microgrammes, it will apply to a reading of not more than 31. 

The previous non-prosecution policy was implemented partly to avoid regular disputes over the accuracy of tests in marginal cases, and the Crown has been criticised for changing this without consultation. Prosecutors will however still exercise a discretion in deciding whether to prosecute borderline cases.

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