The lacing defence: double blind study of thresholds for detecting addition of ethanol to drinks.

In Britain it is a criminal offence to drive if the driver’s measured ethanol concentration exceeds 35 ìg per 100 ml in breath or 80 mg per 100 ml in blood. Those found guilty are disqualified from driving unless they can give a special reason why this should not happen. Most commonly, a defendant claims a friend has “laced” a drink by adding spirits, so that he or she has unwittingly consumed an amount of ethanol sufficient to raise the blood ethanol concentration above the limit. 3 Doctors are sometimes asked in court whether a defendant would have known that a drink has been laced. We conducted an experiment to discover whether volunteers were able to tell that vodka had been added to a drink.