Flashback

20 years ago in Chemistry in Britain

A High Court ruling in August paved the way for motorists to be convicted of drunk driving, even though they may be within the legal limit (80mg per 100ml blood) at the time they are tested, on the basis of back calculations of the level of alcohol in their blood. In a test case in July, a man was convicted for an offence, based on a test over four hours after his car crashed, even though the test revealed 59mg per 100ml blood. Back calculations indicated that the concentration of alcohol in his blood at the time of the incident would have been between 120 and 130mg per 100ml blood. 

The assumption is that an average person metabolises alcohol at a rate of 10-15 per cent per hour (Chemistry in Britain, December 1987). 

Flashback Ed. It would be virtually impossible to obtain a successful conviction today based on the principle of back-tracking. The rates of elimination of alcohol for different people vary greatly and many other factors, including the taking of many medications, would also affect the result and render it open to legal challenge.

An electronic device attached to the car ignition has been developed in the US to prevent a driver who is ’over the limit’ from even starting his car. 

(Chemistry in Britain, December 1987).  Flashback Ed. Some car manufacturers, especially Volvo and Nissan, are currently developing in-car breathalyzer devices, sometimes called ’alcolocks’. Drivers must blow into the device, powered by fuel-cell technology, before the car can be started.