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Two false Fails

Two false Fails

Two false fails

During the hearing at the Supreme Court of Canada into the first version of the IRP scheme, Justice Moldaver mentioned that a second ASD test more or less eliminates the possibility of an inaccurate reading carrying the day. It wasn’t something any of the lawyers picked up to explain. As far as we’re concerned, this is a significant problem with the Immediate Roadside Prohibition scheme. The simple fact is that it is not extraordinary to get two false Fails in a row.

Very important is to understand that even a tiny drop in your mouth can be expected to produce very high readings.

The unanswered question at the Supreme Court of Canada

On May 19, 2015, the hearing took place at the Supreme Court of Canada concerning the legality of the Immediate Roadside Prohibition scheme here in BC. We’ve written about it before and we’re still thinking about how it all unfolded.

IRP driving prohibitions are issued at the roadside by the police based on what they said happened with the Approved Screening Device (ASD) breathalyzer. If you blow a Fail the assumption is that your blood-alcohol content exceeds 80 mg/100 mL. The reading is supposed dictate what the investigating officer will do next.

The subject who blows Fail is entitled to be informed of their right to provide a second sample into a different ASD. The police usually do inform people of this right and most people blow again, meaning in the end they blow two Fails.

Under the first version of the IRP law, the police were under no obligation to notify people of the right to a second test and when they did it usually came with a threat.

At the Supreme Court of Canada hearing into the first version of the IRP law, Justice Moldaver mentioned in his discussion with one of the lawyers that the second sample provisions seem to cover off the issue of a false reading. This wasn’t central to the discussion at that point nor is it central to the appeal, but it concerned us because none of the lawyers still to speak got into the issue and Justice Moldaver more or less answered his own question by suggesting that this was a decent fix to the problems of false readings.

For the sake of those interested, we’ve decided to explain this a little further here on our blog. There are many ways in which two separate ASDs can display two false Fails, but for the sake of today we’ll speak of the big hole in the IRP scheme:

Two false Fails due to mouth alcohol

ASDs were never intended to be used to collect evidence to punish people. They are screeners. The procedures to use them are the procedures for screeners. The presumption is that there will be false readings from time to time but that proper breath tests taken later on will protect drivers from being wrongly punished.

In BC with the IRP scheme the police no longer take proper breath tests to confirm the accuracy of the ASD result. Proper breath tests require several important procedural steps. The first is that the test is taken on an Approved Instrument, which is an evidentiary breathalyzer typically in a police station.

The second and most important step for this discussion is that the subject needs to be observed for 15 minutes before the test to ensure that they don’t get alcohol in their mouth by drinking, burping or any other manner. Why?

Mouth alcohol

Mouth alcohol is the biggest problem with alcohol breath testing. None of the ASDs used in British Columbia can distinguish if the alcohol is related to alcohol in your blood or simply based on alcohol in your mouth. Very important is to understand that even a tiny drop in your mouth can be expected to produce very high readings. Mouth alcohol can come from burping or regurgitation of alcohol from the stomach which is common for people who have heart burn. The obvious source of mouth alcohol is a recent drink. Some scientific studies have detected mouth alcohol 40 minutes after consuming the last drink.

So mouth alcohol is real, and it’s a big problem. One of the procedures that reduces the possibility of false readings when the police take proper breath tests is comparing the two readings. If the readings depart by more than 20 mg/100 mL, then the readings are considered unreliable. That’s great, if your breathalyzer actually tells you the reading.

BC Breathalyzers don’t tell you the reading

The ASDs that we use in BC don’t tell the police the numerical reading. They simply say Fail or Warn when the reading is in an unlawful range. If the first reading is 350 mg/ mL and the second is 200, you know that mouth alcohol was present and the reading was contaminated. But the police don’t know that in BC because they don’t take proper breath tests.

Office demonstration

To prepare to write this post we decided to do a test in the office to remind everyone about the problem of mouth alcohol. First we checked to make sure that our ASDs were functioning properly and within their calibration specs. We checked to ensure that all of our ASDs were in the mode in which they would give us numerical readings as opposed to Fail or Warn.

I put a few drops of scotch in my mouth and after 7 minutes I blew into the first ASD.  The reading was 211 mg/100 mL. Had this device been in the hands of a police officer at the roadside the reading would have been Fail. Keep in mind there was no alcohol in my blood whatsoever.

To properly simulate the test, we then had someone read the second test notification to me. The second ASD was on a different machine. My reading was 145 mg/100 mL.

Again, keep in mind that in the hands of a police officer at the roadside the reading would have been Fail.

It doesn’t matter how the alcohol got there. The point is that mouth alcohol can cause two false Fail readings in a row. A second test is therefore not a guarantee of the reliability of the first test result.

Answering the question posed at the Supreme Court of Canada

So the correct answer to Justice Moldaver’s question is that the procedure used with the IRP scheme provides little if any assurance that the sample is reliable. The threat of mouth alcohol is not safely addressed by taking two tests. You can have two false Fails from mouth alcohol and there is no reason to conclude that this isn’t a common occurrence.


The ASD breathalyzers that we used for the tests mentioned above were an Alco-Sensor IV and and Alco-Sensor FST.

Just for fun I went on to blow three more ASD tests after blowing the second false ASD test. The next ASD I blew into was a Dräger 7410. It’s not a model used in BC, but it is an Approved Screening Device for the purposes of the Criminal Code. My reading was 182 mg/100 mL. Next I blew into an Intoxilyzer 400, also a Criminal Code ASD. My reading was 67 mg/100 mL (a Warn on a BC machine). My final test was with an Alco-Sensor IV and my reading was 68mg/100 mL (again a Warn in BC).


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