"A new review of the alcohol laws in Jersey could see the drink drive limit reduced on the island. It follows calls from some islanders, who want to see the level dropped to a zero alcohol limit. Politicians say that is unlikely but they are welcoming any views on the subject of drink driving."
"There are currently strict alcohol limits for drivers of 35 microgrammes of alcohol per 100 millilitres of breath. That is generally considered to equate to one pint, one medium glass of wine or one measure of spirit, meaning drivers should be under the limit - but that does not account for a person's weight, age, metabolism or even what they have eaten."
"Jersey's Home Affairs minister, Senator Ian Le Marquand says he is against the introduction of a reduction. He said, "This is just something that is being looked at as part of a package, it's a review package. I am personally not in favour of a reduction but it's part of the process and we'll see what views come back." (1)
Margins of Error
One of the problems with reducing the limits is how it will effect the margin of error on breathalyser results. If the margin of error is an absolute, reducing the limits means that the likelihood of error may increase. This is very much what happened in British Columbia in 2010, when stricter drink driving regulations were introduced:
"Under tough new drinking and driving laws enacted in September, B.C. drivers with a blood alcohol level of between .05 and .08 - a warn reading -- face a three-day roadside prohibition and a $200 fine. Blowing .08 and above - a fail reading -- can see drivers without their cars for 90 days and paying fines ranging from $600 to $4,060. Graham said evidence given to him by the RCMP crime lab shows that the calibration on some breathalyzers could be off by as high as one per cent." (2)
Margin of error is often expressed for breathalysers either as a percentage or as a standard deviation. I think the percentage is misleading, because that is based on the ratio of the deviation to the threshold. It is the standard deviation which shows the accuracy, and if the threshold is reduced that remains the same, which means the machine will in fact have a higher percentage of error.
That's not to say the limit cannot be reduced, but it is to note that an awareness of the increased margin of error will result from that, and there is probably a point at which a limit is not really viable.
How do breathalysers work?
"To better understand breath-testing devices, one must have a basic understanding of human physiology and alcohol pharmacology. Alcohol typically enters the body through oral ingestion of a beverage containing ethyl alcohol. Alcohol enters the bloodstream through the stomach and small intestine by simple diffusion"
"Lung tissue is made of air pockets, or alveoli, surrounded by blood-rich membranes. A fraction of the alcohol circulating in the blood crosses the membranes and evaporates into the alveoli. During exhalation, air is forced out of the alveoli and ultimately emerges from the lungs into the person's breath."
This can be calibrated as a result of Henry's Law
"Henry's Law states that in a closed system, at any given temperature, the concentration of a volatile substance in the air above a fluid is proportional to the concentration of the volatile substance in the fluid."
Most enforcement systems use two kinds of breath testing:
"They use preliminary breath testing devices (also known as pre-arrest breath testing devices or "PBTs") and passive alcohol screening devices to identify impaired drivers, evidential breath testing devices (EBTs) to prove their guilt." (3)
But test results can be misleading, and it is a mistake to rely wholly on them. Usually officers involved exercise discretion, and may even require blood testing.
This can be seen in the case of AG v Scott Robert Harben (2007) who was stopped and tested after erratic driving:
"Upon questioning, the Officers formed the opinion that Harben was drunk and conducted a roadside breathalyser test which provided a positive reading of 37 mgs. Harben was therefore arrested and escorted to Police Headquarters where two further breathalyser tests were conducted. Although both samples produced a reading of 33 mgs the Officers were still of the opinion that Harben was unfit to drive."
"During examination, Harben refused to provide a blood and/or urine test. Dr Holmes therefore conducted a physical examination of Harben, observing him to be unsteady on his feet with slurred speech and poor co-ordination, his reflexes were absent and eyes inflamed with grossly dilated pupils. As a result Dr Holmes formed the opinion that Harben was unfit to drive by reason of a combination of alcohol and drugs and assessed his impairment to be equivalent to having a blood/alcohol level in excess of 200mg/100ml if his impairment had been the result of alcohol alone" (4)
Clearly, as G.K. Chesterton observed in "The Mistake of the Machine", it would be a mistake for common sense and observation be discarded on the basis of machine readings. Harben had produced a lower reading when he was evidently unfit to drive, and the officers rightly called for an alternative assessment.
And other factors can falsify breath tests. As a recruit notes (on the States of Jersey Police Website):
"Following the theory we were taught how to use the breathalyser. I was used as the dummy in this exercise and, considering a fail is 35, I shocked the class when I blew 196. Unknown to them I had been given a spray of alcoholic mouth wash! I redeemed myself 20 minutes later when I thankfully blew green."
Obviously, if observation also comes into play, if someone had used an alcoholic mouthwash before going out for an evening, to ensure fresh breath, common sense would show that readings with that much disparity from the state of inebriation expected would be a false positive.
Why Zero Tolerance is not workable
The question: "have you consumed any alcohol?" becomes extremely problematic. The trivial cases of communion wine show up, or eating a few liquor chocolates, or sherry trifle would be consumption of alcohol. This is not however a straw man example that can be dismissed; the very matter arose in Canada, where a ruling by Judge Martin considers precisely this:
"To illustrate, one may consider the following scenario. A driver is stopped at a police checkstop. The officer approaches and asks the driver if he or she has been drinking alcohol, and the driver replies in the affirmative. Using the strict approach, any further questions (even to determine the amount of alcohol actually consumed or the apparent state of the driver's sobriety and ability to drive) would not be permitted, as the time taken to ask and answer the questions would put the demand a few seconds or minutes out of time."
"In other words, every driver suspected of having alcohol in his or her system, even those who had only one drink and would reasonably be considered fit to drive, would nonetheless have their constitutional rights suspended while subjected to a roadside demand and made to provide a breath sample or face a charge for refusing to do so."
"In short, rather than allowing the police officer to make reasonable, preliminary observations to determine whether a roadside demand is warranted or whether the driver is being truthful in claiming he or she had only one or two drinks, all drivers with any alcohol in their system would be tested without an opportunity to explain how much they had to drink or when. That would hardly be an efficient screening system."
"Clearly, a police officer must be allowed the time reasonably necessary to decide whether it is appropriate to make a demand for a breath sample under s. 254(2). This may include questioning to determine whether the driver has alcohol in his or her system as a result of having taken wine at communion, or having spent a day at a bar. No laudable purpose is met by continuing to detain the former driver to require him or her to submit to a roadside screening test."
That I think puts the case in a nutshell. A strict zero-tolerance approach to any alcohol runs into problems over procedure because it has to discount what I have already mentioned - the "reasonable preliminary observations". It is therefore both a waste of police time, and an inefficient means of regulating drink driving.
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