Worth a Try?

Drink-driving offences have resulted over time in a large body of case law. The consequences of a conviction for driving over the limit can be severe, including loss of employment and vastly increased insurance premiums in the future, so it is not surprising that many motorists and their lawyers have wriggled this way and that to find a legal get-out, and it is also not surprising that the higher courts have methodically plugged loopholes as they became evident. So most drivers who fail the breath test plead guilty straight away, and are sentenced pretty much in accordance with the Bench Book guidelines.
Every now and then someone with the resources to hire specialist Counsel and expert witnesses will have a go at one or another technical defence. The last one that I saw relied on a case called Cracknell -v- Willis (1988) which said, in essence, that the reading of the evidential breath machine could be challenged by evidence that the driver had in fact drunk less than needed to justify the machine's reading. To do this there would have to be evidence from the driver and also, preferably from witnesses who could say exactly how much he had drunk. In addition expert evidence is needed to say what his likely reading would have been if he had consumed the amount that he claimed.
In this particular case several witnesses claimed that the man in the dock had sipped abstemiously at no more than a couple of pints, and the expert said that given his weight and the time lapse he would have blown about 15 on the machine, rather than the 66 that appeared on the printout. However, there was no evident fault with the machine, all of the self-checks had been satisfactory, and the printout carried the words 'no errors'.
So he had his day in court, and was duly convicted. That's when we found that he had done something similar a few years ago, so on top of a fine and his enormous lawyers' and experts' bills we disqualified him for three years.
In the post-court debrief, over a cup of tea, we discussed what we had learned. We were a bit surprised that the House of Lords had allowed this challenge to the presumption that the machine is accurate, and the Clerk showed us the full judgment in which one of Their Lordships has dissented, saying that this would create a dangerous precedent, but that he would rely on the common sense of the magistrates. I am sure that very occasionally there will be reasonable doubt that results in an acquittal, but in this case, as one of my colleagues said:- "That alcohol came from somewhere".