Constructor made mistake of law, not fact: convicted of OHSA charge

A constructor that argued the “mistake of fact” due diligence defence was instead found to have made a “mistake of law” and was convicted of a charge under the Occupational Health and Safety Act. 

A construction employee was injured when a large slab of ice fell from the face wall of a water intake tunnel being constructed.  A few minutes before, workmen suspended by a crane in a basket had been chipping away ice from that area.  The constructor was charged with three offences under the Occupational Health and Safety Act.  The second charge, which the Ministry of Labour inspector admitted alleged “technical” safety violations that played no role in the accident, alleged that the constructor failed to ensure that a load rating chart, prepared by a professional engineer, was affixed in a conspicuous place on the crane.

The crane operator admitted that he was “still waiting” to receive the load rating chart from the professional engineer.  As such, the appeal court found that the constructor guilty on the second charge.

The constructor argued the “mistake of fact” branch of the due diligence defence. It argued that there was a rating chart at the base of a removable plywood platform (that is, at the workers’ feet) that was a suitable “variation” on the legal requirement.  It also purported to rely on a “comfort” letter from an engineering firm. The appeal court held, however, that any mistakes the constructor made were “mistakes of law not fact”: the variations were not permissible because the employer had not given written notice to the joint health and safety committee, and the engineering firm’s letter did not refer to the regulation and could not, in any event, displace the requirements of the regulation.  A mistake of law is not a defence.  As such, the constructor was convicted on the rating chart charge.  Two other charges against the constructor were dismissed.

Ontario (Ministry of Labour) v. Dufferin Construction Company, 2014 ONCJ 652


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Adrian Miedema

About Adrian Miedema

Adrian is a partner in the Toronto Employment group of Dentons Canada LLP. He advises and represents public- and private-sector employers in employment, health and safety and human rights matters. He appears before employment tribunals and all levels of the Ontario courts on behalf of employers. He also advises employers on strategic and risk management considerations in employment policy and contracts.

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