Practical jokes rarely seem funny by the time they wind up in Court. The "joke" in a recent case considered by the Court of Appeal (Chell v Tarmac Cement) was about as unfunny as they get. The claimant was a contractor working at a quarry site operated by the defendant company. One of the defendant's employees walked over to the bench where the claimant was working and exploded two pellets (which the employee had brought to work) next to the claimant by hitting them with a hammer. Unsurprisingly, the claimant suffered injuries, including a perforated eardrum and ongoing tinnitus. The issue for the Court of Appeal was whether the company was liable for the actions of its employee (called vicarious liability).
The question that the Court had to consider was whether there was a sufficiently close connection between the employee's employment and their actions. Employers will usually be vicariously liable if an employee was performing their job in an unauthorised way - e.g. if they were responsible for serving customers, but punched a customer in the head when they didn't have the right change. However, if an employee does something unrelated to their employment duties and causes loss to a third party as a result, the employer will not usually be liable, even if it was done on the employer's premises. This distinction can be difficult to draw in practice. (Employers should also note that different rules apply to vicarious liability for breaches of discrimination and whistleblowing law - the Court was dealing here with vicarious liability for negligence.)
In this case, the Court held that the employer was not vicariously liable for the employee's actions. The real cause of the injuries was the explosive pellet, which wasn't the employer's equipment and the use of which formed no part of the employee's duties. It couldn't be said that he was carrying out his job but in an unauthorised way - he was engaged in a 'frolic of his own'. Likewise, the employer was not liable for a breach of health and safety requirements - there was no reasonably foreseeable risk of injury which the employer had failed to take steps to prevent. Even if the employer had been under a duty to prevent the incident, it had done all it reasonably could by having site rules in place and a clear disciplinary policy.
A key takeaway here for employers is to have clearly-defined roles for employees, so that when they step outside the bounds of their role, it's less likely that the employer will be liable for any resulting losses. At the same time, clear standards of conduct and robust safety rules are essential. And perhaps quizzing job applicants on their sense of humour wouldn't go amiss.