HC Deb 24 January 1968 vol 757 c146W
Mr. Haseldine

asked the Secretary of State for the Home Department how many cases of a positive breathalyser test have ultimately shown that a person arrested had a blood-alcohol content well below the prescribed limits and was innocent of any offence.

Mr. Taverne

Of 1,576 such cases in which blood or urine specimens were analysed up to the end of last November, there were 344 in which the specimen was not certified as proving a blood-alcohol concentration exceeding the prescribed limit. This does not necessarily mean that the concentration was less than the prescribed limit at the time when the breath test was made, or that ability to drive was unimpaired.