The ASD – How It Works

The Approved Screening Device, formerly called the Roadside Screener, is intended to provide a quick and easy way for the police to assess a driver’s sobriety without detaining them for a lengthy investigation.  Alcohol from the sample of breath is oxidized becoming acetic acid, then generating an electrical current which is measured and interpreted by the internal software.

History of Approved Screening Devices

In 1975 the Criminal Code was amended to allow officers to compel a suspected impaired driver to undergo a roadside screening test.  It had become clear that police officers often lacked the ability to identify dui and dwi drivers.  At the time studies showed that in the early morning hours the driver of 1 in 8 vehicles was dwi.

One of the first devices approved by Parliament to screen dui and dwi cases was the A.L.E.R.T. Alcohol Level Revaluation Road Tester.  The device was calibrated to show a red light if the subject blew over 100mg in 100ml, amber if between 50mg and 99mg in 100ml and green if 49mg and below.

Ultimately the device was discredited mainly due to the possibility of interference by substances other than alcohol and technological advances that made it obsolete.
The A.L.E.R.T. was believed to be accurate five minutes after the last alcohol consumed. We now know that a false fail is very likely, even if the last drink was 15 minutes earlier.  It is likely, therefore, that many people were wrongfully convicted on the evidence of an A.L.E.R.T. “Fail.”

Screening devices now commonly used in British Columbia, such as the Alco-Sensor IV DWF Screener, have the capacity to display the actual blood/alcohol concentration.  However, the software in the Alco-sensor screener retains “Fail” and “Warn” as the display messages.  The risk is that a subject who is under 0.08 mg% with a miniscule amount of alcohol in their mouth may blow 0.101 mg% and the officer will only know it as a “Fail.”