Autrefois attaint is a plea in a criminal case that the defendant has already been attained for one felony, and therefore cannot be prosecuted for another felony. It is an early day plea.
The following is an example of a case law referring to the autrefois attaint:
Under an early practice in England where attainder was consequent on conviction of felony, the doctrine that a plea of autrefois attaint was a bar to prosecution for another felony of the same grade obtained for the reason that a second trial would be wholly superfluous, but where the punishment was more severe for the second offense the plea would not prevent it. In the United States, the doctrine is obsolete and h hence a conviction and sentence for one felony is not a bar to an indictment or trial for another and a convict while imprisoned in the penitentiary is not exempt from trial and sentence for another crime whether charged to have been committed before or during such imprisonment. [Blitch v. Buchanan, 100 Fla. 1202, 1218 (Fla. 1930)].