What does 'Novus Actus Intervenien' mean in causation?How does it apply?

'Novus Actus Intervenien' (NAI) essentially means an intervening act. This applies after you have gone through the stages required for Factual causation and Legal causation. You will know that a NAI applies when there is either a third party involvement, the victim own act interferes or when there was a natural but somewhat unpredictable event that has occured. For a NAI to be successful, it must show that the defendant is not responsible for the consequence (which in most cases will be some form of injury).