This was a common law principle applied in criminal law which says that inorder to constitute murder, the death must occur within one year and one day of the act or omission alleged to cause the death. If the death occurred afterwards it was conclusively presumed not to be murder.
Although the rule has been judicially abrogated in a number of jurisdictions in US, none of those courts have adopted a new time limit to replace the year-and-a-day rule. In declining to do so, courts emphasize that no arbitrary time frame is needed because abolition of the year-and-a-day rule does not relieve the State of its burden of proving causation beyond a reasonable doubt. [State v. Rogers, 992 S.W.2d 393, 398 (Tenn. 1999)]
This principle is no longer in force in England. It was abolished by the Law Reform (Year and a Day Rule) Act 1996. With the great advances made by medical sciences, the successful intervention of doctors prolonged the life of the victim and this prevented murder prosecutions.