Photo: The Canadian Press

Minister of Justice and Attorney General Jody Wilson-Raybould

The foremost constitutional authority in Canada once argued that random breath testing — similar to what the Liberals proposed to crack down on impaired driving — would infringe Charter rights, but the benefit to public safety would be so strong that it would still be upheld in court.

Toronto-based lawyer Peter Hogg concluded nearly seven years ago that the ability of police to demand a breath sample from motorists at random, even without reasonable suspicion they drank alcohol before getting behind the wheel, would be a reasonable limit on constitutional rights and freedoms.

"I am confident that a constitutional challenge would be unsuccessful," Hogg wrote in August 2010 after MADD Canada asked him to weigh in.

The Liberal government introduced Bill C-46, which includes new powers for police and harsher penalties for driving under the influence of alcohol or drugs, in the House of Commons last month alongside their long-awaited plan to legalize marijuana for recreational use.

The bill is expected to come up for second reading Friday.

The proposed law includes new mandatory alcohol screening measures that would allow police to demand a breath sample from any driver they lawfully stop even if they had no suspicion the person had been drinking before being pulled over.

MADD Canada has long been pushing for some version of the legislation. Other countries that have taken a similar approach, including Australia, New Zealand and Ireland, have seen a substantial reduction in alcohol-related accidents and even deaths, they argue.

It was in this context that the advocacy group asked Hogg to review a draft of an article co-authored by Robert Solomon, its national director of legal policy and a law professor at Western University in London, Ont.

It dealt only with random breath testing for alcohol consumption, but not with drug testing or any other measures included in the current bill.

Hogg agreed with the conclusion that random breath testing, which the Conservative government had also explored, would not violate Section 8 of the Charter of Rights and Freedoms, which protects against unreasonable search and seizure.

"The invasion of the driver's privacy is minor and transitory and not much different from existing obligations to provide evidence of licensing, ownership and insurance," Hogg wrote.