The Liberal government will soon table a defense of its sweeping reforms on drug and alcohol-impaired driving in Canada.

The charter statement will explain why Justice Minister Jody Wilson-Raybould believes the legislation upholds Canadians' constitutional rights. It was scheduled to be tabled in the House of Commons Wednesday afternoon, but has been delayed due to a late change in the minister's schedule.

The bill was tabled last month at the same time as legislation to legalize marijuana, and includes tougher penalties and new powers for police to demand mandatory roadside breath samples. The government has maintained it is charter-proof, but many legal experts say new provisions go too far and violate fundamental rights.

Edmonton-based defence lawyer Steve Smith expects the bill will face a swift series of challenges, of which many will be successful. One of the biggest will come to a proposed mandatory roadside breath sample, on the grounds it breaches Section 8 of the Charter of Rights and Freedoms, which protects against unreasonable search and seizure.

The bill could ultimately "rise or fall" under a test around Section 1 of the charter, which allows imposed limits to an individual's rights as justified for the public good, Smith said.

Right now, an officer must have reasonable grounds to suspect a driver is impaired before demanding a breathalyzer. Under the bill, anyone could be required to blow after being lawfully stopped in their car.

Mandatory breath sample

"They can make a demand for a breath sample without having any reason to believe there is any alcohol in the person's body at all. They can do essentially random roadside tests on drivers," Smith said.

The government has said the goal is to nab more people who are now managing to elude detection, and also to reduce legal action over whether an officer actually had reasonable grounds for suspicion to demand the breathalyzer.

But Smith believes the legislative overhaul will lead to more legal action, adding to the problem of widespread court delays.

"I find it very interesting that the government, which is apparently so concerned about courts being overburdened and cases being overturned and stayed as a result, has decided to overhaul one of the most frequently litigated and complex areas of the law, which is going to have the effect, at least in the short term, of dramatically increasing litigation in this area."

The federal government plans to make cannabis legal by July 1, 2018. MADD Canada says the problem of drug-impaired driving will become worse when cannabis becomes legal. (Jim Young/Reuters)

To confront drivers impaired by pot or other drugs, the legislation allows police to demand a driver provide a saliva sample if they suspect he or she is impaired by drugs. A positive reading could lead to further testing, including a blood test.

Smith said there's a potential challenge there, if scientific evidence shows having a specified level of TCH in the system may not match to level of impairment.

Other challenges could come to some technical elements of the bill, including one about being over the legal limit of alcohol within two hours of stopping a motor vehicle, and an accompanying rule that puts the onus on the accused to prove what alcohol was consumed since the vehicle was stopped. They could be tested under Section 7 of the charter, which protects a person's right to life, liberty and security.

Strong deterrent

Robert Solomon, a law professor at Western University in London, Ont., and the national legal policy director for MADD Canada, said there is no doubt the new legislation will face challenges, including "frivolous" ones. But he believes the bill is on solid constitutional footing.

Canadians are already subject to mandatory searches at airports, courthouses and border crossings, Solomon noted.

He said many countries already allow mandatory roadside testing because research shows the risk of apprehension is a strong deterrent for drunk drivers.

"It is widely seen as the most effective way of reducing impaired driving deaths," he said.

No matter what provisions or penalties are put in place, Solomon predicts the problem of drug-impaired driving will become worse when cannabis becomes legal.

"It's a huge increase in availability, and invariably there's going to be more stoned drivers on the road," he said.

The government plans to make marijuana legal by July 1, 2018.