Can police breathalyze you for no reason?

In Canada, yes, with limits. Since December 18, 2018, section 320.27(2) of the Criminal Code lets a police officer who has an approved screening device demand a breath sample from a driver without suspecting alcohol. The officer must have stopped you lawfully first, and it applies to someone operating a motor vehicle, not at home.

This page answers for Canada and Ontario. Some answers online are written for other countries. If you were charged after a roadside test, see what each paper means. Charged is not convicted.

Since 2018, police need no suspicion to demand a roadside breath sample.

The Criminal Code calls it "Mandatory alcohol screening". Under section 320.27(2), a peace officer who has an approved screening device may, while lawfully using their powers, demand that the person operating a motor vehicle give breath samples into that device right away, and go with the officer to do it.

Justice Canada puts it plainly: it applies "whether or not they suspect that the driver has recently consumed alcohol".

In plain words, the officer doesn't need to smell alcohol, see a swerve or hear about a drink first. A lawful stop and the device in hand are what the section asks for.

The change came into force on December 18, 2018, with the rest of the new alcohol impaired driving law.

Sources: Criminal Code s. 320.27(2), laws-lois.justice.gc.ca; Justice Canada, news release, December 4, 2018.

The stop itself still has to be lawful.

"No suspicion" is not "no rules". The section only works while the officer is lawfully using powers they already have, under federal law, provincial law or the common law.

In Ontario, the Highway Traffic Act gives one of those powers. A police officer, readily identifiable as one, may require a driver to stop to check whether there is evidence to justify a breath demand under section 320.27 or 320.28 (HTA s. 48(1)).

Justice Canada says screening "would only be done after the person has been lawfully stopped, under common or provincial law".

So there are two questions, not one. Could the officer demand the sample? And was the stop lawful in the first place? The first is in the Code. The second depends on the facts of your night.

Sources: Criminal Code s. 320.27(2); Highway Traffic Act, s. 48; Justice Canada, questions and answers.

The officer must have the screening device at hand.

Section 320.27(2) is for an officer who has an approved screening device in their possession. The Code defines it as a device designed to ascertain the presence of alcohol in a person's blood, approved by the Attorney General of Canada (s. 320.11).

Justice Canada lists all three conditions together: screening "can only be used if the driver is operating a vehicle, the vehicle has been lawfully stopped, and if the police officer has the approved screening device at hand".

A screening result can lead to further steps. Those belong to 320.14(1)(b), over 80. The roadside licence suspension has its own page: Your paper says 90 days.

Sources: Criminal Code s. 320.11, laws-lois.justice.gc.ca; Justice Canada, questions and answers.

It is for drivers on the road, not once you're home.

The section speaks of the person who is operating a motor vehicle. Justice Canada adds that screening "does not apply when drivers have returned home or arrived at their destination".

That is the limit of mandatory screening. It is not a statement about every other power police have.

Source: Justice Canada, questions and answers.

Other roadside demands still need a suspicion.

Section 320.27 has two parts.

Subsection (1) needs a suspicion. With reasonable grounds to suspect alcohol or a drug in your body, and that you operated a vehicle within the last three hours, an officer may demand physical coordination tests, screening breath samples, or a sample for approved drug screening equipment.

Subsection (2) does not. That is the breath screening this page is about.

The drug and coordination side belongs with 320.14(1)(a), impaired.

Source: Criminal Code s. 320.27(1), (2).

Courts have upheld these stops, and over 40 countries use screening.

Justice Canada: "The Supreme Court of Canada has previously upheld these types of traffic stops as lawful." It cites R v Hufsky (1988) and R v Ladouceur (1990). It also says mandatory alcohol screening is authorized in over 40 countries.

That is about the law in general. It says nothing about one stop on one night.

Source: Justice Canada, questions and answers.

Refusing a demand is a separate offence.

Refusing or failing to comply with a demand is a separate criminal offence, s. 320.15. If that is the line on your paper, start at 320.15, refusal.

The questions about the stop go to court, not to the roadside.

A roadside demand, a screening result and a charge are three different steps. Only the charge puts a court date on your paper, and a charge is not a conviction. Whatever happened at the roadside, including whether the stop was lawful, the case itself is decided in a courtroom. The date and the building are on your paper. Which courthouse is on your paper?