This is an expression used by TAC lawyers to describe a situation where the TAC seeks to discount a seriously injured person’s common law damages because the person was not wearing a seat belt at the time of the accident. The TAC has to establish that the person’s injuries would not have been as severe if a seat belt had been worn. The TAC bears the burden of proving this. A seat belt defence can give rise to a finding of contributory negligence on the part of the accident victim and as a consequence the person’s damages are reduced by the extent to which their own negligence contributed to their injuries. There is no set or fixed percentage reduction and every case is assessed on its own facts.