Case in Brief

A Case in Brief is a short summary of a written decision of the Court, drafted in plain language. These summaries are prepared by staff of the Supreme Court of Canada. They do not form part of the Court’s reasons for judgment and are not for use in legal proceedings.

R. v. Larocque

Case summary

The Supreme Court of Canada says the Crown does not have to prove the target value used in a breath test.

This case is about what the Crown must prove to use breath test results in a drunk driving case. Breath testing machines are checked regularly to make sure they work properly. Before using the breath machine, the technician checks it with an alcohol standard, which is a solution with a known amount of alcohol. The machine should produce a result close to that known number, called the target value.

When stopped by police, Mr. Larocque provided two breath samples that showed a blood alcohol concentration above the legal limit. He was charged with drunk driving.

At trial, the Crown presented certificates from the qualified technician and from analysts to show the breath test was done correctly. The judge found him guilty. The summary conviction appeal judge (a higher-level judge) and the Court of Appeal both agreed with that result. Mr. Larocque then appealed to the Supreme Court of Canada.

The Supreme Court dismissed the appeal.

The certificate from the breath technician is enough evidence.

Writing for the majority, Justices Rowe and Moreau said that while the Crown must share the target value with the defence, it does not have to prove that value in court. Parliament did not mean to make the target value itself a legal condition that must be proven before using breath test results. What matters is that the qualified technician confirms that the machine’s test result was within 10% of that target number.

Justices Rowe and Moreau explained that making the Crown prove the target value would add technical steps that go against Parliament’s goal of keeping impaired-driving cases simple and efficient. The law already says that a qualified technician’s certificate can be used as proof of its contents. That means if the certificate says the calibration check result was within 10% of the target value, the Crown has met that requirement.

In this case, the Crown’s certificate said the qualified technician did the calibration check properly and that the result was within 10% of the target value. Because the alcohol standard used in that test was certified by an analyst, the Crown could rely on it.

For these reasons, Mr. Larocque’s conviction was maintained.