Mandatory Alcohol Screening: Unreasonable Search or Demonstrably Justified?

Author(s): Beirness, Davis
Mavis Johnson Traffic Safety Award

Slide Deck Presentation:

Beirness CARSP MAS



This paper examines Mandatory Alcohol Screening (MAS) as a means to reduce the number of deaths and injuries associated with operating a vehicle while impaired by alcohol. MAS was introduced in Canada in December 2018. It allows police officers to request a breath sample from any driver who is legally stopped, even in the absence of suspicion the driver has been drinking.

MAS is founded on the theory of general deterrence which indicates that increasing the probability that drinking drivers will be detected by the police serves to lower the probability of the behaviour occurring.

MAS (also known as Random Breath Testing or Compulsory Breath Testing) has been used throughout Europe, Scandanavia, Australia and New Zealand for many years. There exists considerable evidence of the effectiveness MAS in reducing alcohol-involved crashes. Nevertheless, there remains concern about MAS being a violation of the right to be free from unreasonable search.


The purpose of this paper is to explore the rationale, purpose and initial impact of MAS in Canada as well as some of the objections to it. Using research evidence from a variety of studies, this paper illustrates the challenges of detecting alcohol in a brief interaction with a driver at roadside, the value of more frequent alcohol checkpoints and mandatory alcohol screening in changing the prevalence of driving and drinking and alcohol-involved crashes in Canada.

Target Group:

The program is targeted at both the police and drivers. The police need to embrace the concept of general deterrence and commit to using MAS on a routine basis. Drivers need to be convinced there is an increased probability that they will be stopped and tested for the presence of alcohol as a means to reduce the prevalence of driving after drinking.


The paper outlines MAS legislation in Canada and the implementation of MAS by the Edmonton Police Service. Data will be presented on the results of impaired driving enforcement operations in the three years prior to MAS and in the first year following the introduction of MAS.

Objections to MAS have prompted challenges to the law. Some argue that simply increasing the number of alcohol checkpoints would also serve to enhance deterrence and reduce crashes. Others say the procedure is an inconvenience that causes undue delay and is an inefficient means of detecting impaired drivers. Other point to a violation of the right to be free from unreasonable search and seizure and an increased opportunity for racial profiling by the police. Each of these objections will be examined.


Understanding the rationale and objectives of MAS by both the general population of drivers as well as the police is an important factor in the success of MAS. Sharing the information from this study with the police and the general public will serve to enhance the understanding of the rationale and purpose of MAS and help gain more widespread acceptance. As MAS is rolled out in the post-pandemic period, it is expected that the impact of MAS in reducing the number of motor vehicle crashes involving a drinking driver.