In a 2016 trial, R. v. Gallant, an Ontario Court judge found that the possibility of bolus drinking raised reasonable doubt that the accused woman was guilty of drunk driving. This case concerned a woman who was involved in a single-car collision and was subsequently charged with impaired driving and ‘over 80’ (for operating a vehicle with over 80 milligrams of alcohol per 100 millilitres of blood). 

What is Bolus Drinking?

The bolus drinking defence is based on the understanding that when a driver consumes a significant amount of alcohol just before driving, the recently-consumed alcohol is not immediately absorbed into the bloodstream and as a result, their blood alcohol concentration (BAC) may be under 80 milligrams of alcohol in 100 millilitres of blood while driving. In Gallant, the key issue to be decided was whether there was a reasonable doubt that the accused woman consumed the majority of the alcohol either just before, or after driving. 

Case Background

Ms. Gallant’s accident occurred near Bloor and Dundas in Toronto, at about three in the afternoon. She told officers at the scene that the accident resulted when she swerved to avoid a cat. An officer who was flagged down by a civilian and first on the scene did not notice any signs of impairment, such as difficulty walking or the smell of alcohol on the driver’s breath, in the short time that he interacted with the driver. The officer who next arrived (at 3:34 p.m.), later testified that Ms. Gallant’s eyes were glossy and bloodshot and her face was flushed, she was slow to exit the car and appeared unfocussed, and her breath smelled of alcohol. Based on a belief that there was reasonable suspicion that the driver had consumed alcohol, the (second) officer made an ASD demand, which she failed. In his search of Ms. Gallant’s car, the officer found a purse and despite her objections, he opened her purse and found an opened 26-ounce bottle of vodka, with a quarter to half missing. 

Analysis and Findings

After failing a roadside approved screening device test, the woman was arrested and taken to the police station, where she gave two breath samples which registered 357 milligrams and 350 milligrams of alcohol, respectively, in 100 millilitres of blood. These samples were taken at 4:46 and 5:11 p.m. Once the results of the breath tests became known, the officers charged Ms. Gallant with impaired driving, as they believed her BAC readings along with other evidence indicated that her ability to operate a motor vehicle was impaired by alcohol.

Evidence introduced at trial included the testimony from two arresting officers, a qualified Intoxilyzer technician, and the forensic toxicologist. The court also reviewed video evidence from the scene as well as from the police station.

The toxicologist for the Crown testified that, on the assumption that Ms. Gallant was driving at 3:45 p.m., her BAC would have been between 350 and 405 milligrams of alcohol at the time. The toxicologist surmised that Ms. Gallant’s BAC would have been even higher if she drove earlier, and a person could even die when having consumed that much alcohol. The toxicologist stated that her opinions on BAC were independent of gender or age, and were based on four assumptions. Two of these assumptions are relevant to this case: one is that the accused did not consume a large amount of alcohol just before driving (i.e. bolus drinking), and the second is that she did not consume alcohol after driving. The toxicologist was also asked how much alcohol someone would have consumed in the 15 minutes before driving or shortly afterward, to not exceed 80 milligrams at the time of the accident but still produce the BAC readings obtained for Ms. Gallant. She responded that a 100-pound woman must consume 7.5 ounces of alcohol, such as vodka, to not exceed 80 milligrams at the time of driving.

Justice Borenstein expressed a certain belief that Ms. Gallant was impaired and also had a ‘dangerously high’ BAC when she was tested at the station. However, the issue of merit in deciding this case was whether there was a reasonable doubt that the accused drank 7.5 ounces of vodka or more, in the 15 minutes before driving or after the accident. Given that 6.5 to 13 ounces of alcohol were missing from the vodka bottle in Ms. Gallant’s purse, there was an opportunity for her to have done so.

The toxicologist’s report was based on the assumption that there was no bolus drinking. The courts have generally acknowledged that bolus drinking is a relatively rare occurrence and people do not normally consume large quantities of alcohol immediately prior to, or while, driving (R. v. Paszczenko (2010)). Nevertheless, the Crown is in a difficult position of having to prove a negative in order to establish that an accused has not been involved in bolus drinking. Often, such cases are further challenged by a lack of witnesses or evidence on the accused’s drinking behaviour at the relevant time. 


In this case, the Crown argued that it is not reasonable to speculate that Ms. Gallant drank 7.5 ounces of vodka or more immediately before or after driving (and before her blood alcohol test). However, Justice Borenstein disagreed, noting that although it may be unlikely that she drank this amount, there was reason to believe that bolus drinking may have occurred, based on the following circumstances.

  • The first officer on the scene observed no signs of impairment.
  • There was 6.5 to 13 ounces of alcohol missing from the accused’s vodka bottle.
  • Ms. Gallant attempted to prevent the officers from finding the vodka bottle.
  • She had time and access to an open bottle of vodka, which created a real possibility that she consumed vodka while and/or just before driving.
  • The open bottle of alcohol in the car is a potential indicator of abnormal drinking.

Also, although the accident may be evidence of impairment, Justice Borenstein stated that the possibility that Ms. Gallant swerved to avoid a cat, as told to the arresting officers, is a potential and innocent reason for her collision. Further, the general lack of evidence on the cause of the accident and the uncertainty on the rest of the evidence raises a reasonable doubt on the issues in this case. Although Justice Borenstein thought it likely that the accused did not drink 7.5 or more ounces of alcohol, he acknowledged that there was nevertheless a possibility of bolus drinking. Concluding that the Crown had not proven the charges of impaired driving and ‘over 80’ beyond a reasonable doubt, Justice Borenstein ruled that the accused must be found not guilty.

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