Apparently when it occurs on a business trip...
An Australian public servant is suing her employer for compensation after being injured while having sex during a business trip.

She works for ComCare, the Australian government’s—wait for it—workplace safety organization. During sex (not, for the record, part of her job) with a male friend (not connected to her job) a glass light fitting tore from the wall above the bed and struck her face. The woman, who cannot be named, suffered injuries to her nose, mouth, and a tooth, as well as “a consequent psychiatric injury,” described as an adjustment disorder, according to Australia’s Daily Telegraph.

ComCare originally rejected her claim for the November 2007 incident, saying that sexual activity was not an ordinary part of an overnight stay, such as showering or sleeping. (She was staying in a motel because of a business meeting she had the next day.) So the woman sued.

Her lawyer, Leo Grey, told a federal court there was no suggestion she’d engaged in misconduct. Her injury, he said, occurred during “an ordinary incident of life commonly undertaken in a motel room at night.” He pointed out that “there had not been any rule that employees should not have anyone else in their room without express permission of their department.”

ComCare has argued that “neither legal authority nor common sense” could find the injury was sustained during the course of her employment.

Observes US workers comp management consulting firm Lynch Ryan on its blog: “From the American litigation perspective, it might seem more logical to sue the hotel or the light manufacturer. But as Australia's comp law—unlike the American statutes—does allow compensation for pain and suffering, a liability claim might not add anything to the
potential payout.”

Could it be considered a work injury if the man had been a work acquaintance? It “might have been compensable,” observes the blog. “The devil, as always, is in the (salacious) details.”
When Does Sex Count as a Work-Related Injury? | Inc.com