Ontario judge rules legal limit for THC impairment is constitutional

May 12, 2022

Earlier in April, a Brampton judge overseeing the trial of a driver who struck and killed a woman and her three young daughters in a 2020 crash has rejected his challenge of the law on cannabis-impaired driving.

Last year, Brady Robertson had pleaded guilty to four counts of dangerous driving causing death in connection with the June 18, 2020 collision resulting in the death of Karolina Ciasullo and her three daughters. However, he had pleaded not guilty to four counts of operation while impaired by drugs causing death, and his lawyers filed a constitutional challenge of Canada’s law setting out a legal limit for THC blood concentration when driving. Specifically, Robertson’s lawyers argued that the legal limit of five nanograms of THC per millilitre of blood is arbitrary, overboard, and does not correspond to impairment.

In addition, Robertson’s defence lawyer Mayleah Quenneville argued that limit runs the risk of not only catching people engaging in risky behaviour but also those “morally innocent” people who use cannabis for medical reasons, and who use responsibly but still have residual THC in their blood. Moreover, his defence lawyers also noted the possibility that frequent cannabis users could have residual THC levels beyond the legal limit, despite not being impaired when tested.

Ontario court Judge Sandra Caponecchia had provisionally convicted Robertson on four counts of impaired driving causing death, after it was determined that Robertson had a blood THC concentration of 405 ng/ml about 45 minutes after the crash, but noted that the verdicts were “subject to the outcome of the constitutional challenge.”

In a subsequent ruling in April, Judge Caponecchia rejected that challenge after determining that the legal limit complies with Robertson’s charter rights.

Furthermore, she noted the challenge raises “complicated policy considerations,” concluding that although the legal limit may affect some frequent and chronic users of cannabis, “it does so in a way that does not violate the principles of fundamental justice because on balance, the impact is neither arbitrary, nor overboard.”

“The impact is consistent with Parliament’s stated intention when the possession of cannabis was legalized: to strengthen the laws with a view to not only detecting impaired drivers but also deterring individuals who consume cannabis from getting behind the wheel of a car when they represent a risk to the public,” states the ruling.

In her ruling, the judge also said it cannot be assumed that a THC reading of 5ng/ml reflects a “harmless amount of residual THC level,” in contrast to the evidence of recent consumption, in every frequent cannabis use. “Blood can only be seized when there are reasonable grounds to believe an offence has been committed,” the judge concluded.