Common Law Duty of Care: Can a Mechanic Be Liable for Releasing an Unsafe Vehicle?

Sara Santos-Vigneault
Jun 17
3 min read

Two mechanics work in a garage. One inspects a lifted car; the other welds a red car, sparking brightly. Tool shelves and signs fill the space.

In Canada, automotive repair shops aren’t just service providers—they are legally responsible for ensuring the vehicles they service are safe for the road. While most people understand that mechanics repair cars, fewer realize that they also carry a legal duty to act with reasonable care. This obligation is known as the common law duty of care, and breaching it—even without a formal contract—can lead to serious legal consequences.

This article explains what this duty involves, when it arises, and what legal implications may follow if it's ignored.

What Is the Common Law Duty of Care?

The common law duty of care is a principle developed through court decisions rather than legislation. It is central to the law of negligence, which governs situations where someone's actions—or failure to act—cause foreseeable harm to others.

For mechanics and repair shops, this duty means they must:

Perform repairs competently
Identify and disclose safety-related defects
Avoid returning unsafe vehicles to customers

A failure in any of these areas can result in liability for negligence if someone is injured or property is damaged.

When Does This Duty Arise for Mechanics?

The duty of care is triggered when a mechanic or repair facility accepts responsibility for working on a vehicle. This applies whether or not there is a written contract and may extend to individuals other than the vehicle owner, such as passengers, pedestrians, or other drivers.

The Supreme Court of Canada articulated the legal framework for establishing a duty of care in Cooper v. Hobart, 2001 SCC 79. The Court’s two-part test includes:

Foreseeability and Proximity: Was the harm reasonably foreseeable? Is there a close enough relationship between the parties?
Policy Considerations: Are there reasons in public policy or law to limit or deny the duty?

In most automotive repair situations, both criteria are met.

Reference: Cooper v. Hobart, 2001 SCC 79 https://www.canlii.org/en/ca/scc/doc/2001/2001scc79/2001scc79.html

Why Is This Duty Important?

If a mechanic negligently returns a vehicle in unsafe condition and it causes harm, the shop could be held liable. Common examples of negligent conduct include:

Failing to properly repair or identify faulty brakes
Overlooking worn or damaged steering components
Ignoring dashboard safety warnings or critical system failures

If an incident occurs and the shop is found to have acted negligently, they may face financial liability, legal claims, and reputational damage.

Relevant Case Law

Donoghue v. Stevenson, [1932] AC 562

This British case laid the foundation for modern negligence law by introducing the “neighbour principle.” It states that individuals must take reasonable care to avoid acts or omissions that could harm those closely affected by their actions.

Reference:Donoghue v. Stevenson, [1932] UKHL 100 https://www.bailii.org/uk/cases/UKHL/1932/100.html

Cooper v. Hobart, 2001 SCC 79

This Canadian decision established the two-part test for determining whether a duty of care exists. It remains a key precedent in negligence cases.

Reference:Cooper v. Hobart, 2001 SCC 79 https://www.canlii.org/en/ca/scc/doc/2001/2001scc79/2001scc79.html

Rankin (Rankin’s Garage & Sales) v. J.J., 2018 SCC 19

In this case, a minor was injured after stealing an unsecured car from a garage. The Supreme Court held that no duty of care was owed in that specific context, but emphasized that foreseeability remains the core question when assessing liability.

Reference:Rankin (Rankin’s Garage & Sales) v. J.J., 2018 SCC 19 https://www.canlii.org/en/ca/scc/doc/2018/2018scc19/2018scc19.html

How This Applies to Repair Shops

To reduce legal risk and uphold safety standards, repair facilities should:

Clearly inform customers about safety-critical issues
Get explicit consent before performing additional or costly repairs
Avoid releasing vehicles that pose a danger to road users, even if the customer insists
Keep records of customer communications and recommendations
Provide written warnings if a vehicle is released in a less-than-safe condition due to customer refusal to authorize further work

In Ontario, the Consumer Protection Act, 2002 also requires mechanics to obtain customer authorization for additional work beyond the original agreement.

Reference:Consumer Protection Act, 2002 https://www.ontario.ca/laws/statute/02c30

Legal and Practical Significance

This duty of care is more than a business best practice—it’s a legal obligation. Releasing an unsafe vehicle could endanger lives and result in serious legal consequences for the mechanic or shop involved. Canadian courts consistently hold that where harm is foreseeable, and a party had a duty to prevent it, negligence liability may arise.