In The Hospice of St Mary of Furness v Howard the EAT held that, whilst it is not necessary for a claimant to establish the cause of an alleged physical impairment, in such a case a respondent can seek to disprove the existence of that impairment by calling evidence to show either that the impairment is not genuine, or that the claimant is in fact suffering from a mental, not a physical, impairment.

In this case the parties had jointly instructed a medical expert who concluded that the claimant suffered from a back complaint, despite an MRI scan revealing nothing and it not being possible to make a precise diagnosis. The EAT permitted the respondent, which had failed to elicit further information by putting questions to the jointly-instructed expert, to instruct a further medical expert. It held that the respondent had a good (as opposed to a fanciful) reason for wanting to do so; it wished to argue that the claimant's symptoms were either not genuine, psychogenic or could not be said to be substantial or long-term. Further, given that the claimant had served a schedule of loss in the region of £500,000, the additional expense and delay that would arise from a further expert being instructed was not disproportionate in the circumstances of the case.