OTTAWA -- 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.

Hogg said by email Wednesday that while his 2010 arguments might need some "updating tweaks," his basic opinion has not changed.

Justice Minister Jody Wilson-Raybould has disagreed with Hogg on other issues before, notably when he concluded the Liberal doctor-assisted death law was inconsistent with the landmark Supreme Court decision that struck down the previous ban.

But when it comes to Section 8, Wilson-Raybould actually made a similar argument in the so-called "charter statement" she tabled in the House of Commons last week.

Still, while Wilson-Raybould defended measures as permissible under the charter, Hogg did not.

He found that random breath testing would go against section 9, regarding arbitrary detention and imprisonment, as well as section 10(b), which is the right to see a lawyer without delay.

But, he argued, those infringements meet the criteria for being justified under section 1, which allows the government to bring in a law that places reasonable limits on Charter rights, so long as, among other things, it can prove the goal was important enough to warrant such an overreaching.

"The objective of (random breath testing) is to increase safety on the roads, or, more specifically, to reduce the carnage caused by impaired driving," Hogg wrote.

There is another big difference: Hogg was referring only to random stops, such as at a checkpoint.

That is narrower than what Bill C-46 would allow.

"(Random breath testing) will typically be applied to every driver passing through a checkpoint, so there is no stigma or humiliation involved, and no singling out of individuals on improper grounds (such as racial profiling)," Hogg wrote.

Josh Paterson, executive director of the B.C. Civil Liberties Association, called that an important question now that there is more awareness about allegations of systemic discrimination that can accompany random police stops.

"When you start to think about the various ways in which police stops on foot are not random in lots of circumstances and disproportionately affect communities of colour, racialized minorities -- when you put that lens over this whole thing, I think it raises cause for concern," said Paterson.

On Wednesday, Wilson-Raybould said "the potential for racial profiling" did come up as the legislation was being drafted, but added she does not think it would come into play.

"There is nothing inherent in the new legislative power to use mandatory alcohol screening that creates a greater risk of racial profiling," she said in an emailed statement.

"It would not give police any more powers than they already have under common or provincial law to stop drivers at random to determine their sobriety.

"Importantly, mandatory screening would not alter the responsibility that law enforcement has towards training and oversight to ensure fair and appropriate application of the law to all Canadians, free from racial and other forms of bias."