The article below explained the legal meaning of Autrefois Convict and Acquit.
A plea of “autrefois convict” (Previously Convicted) is one in which the defendant claims to have been previously convicted of the same offence with the same “facts” and that he or she therefore cannot be tried for it again.
A plea of “autrefois acquit” (Previously Acquitted) is a defendant’s plea stating that he or she has already been tried for and acquitted of the same offense with the same facts . For this plea to be successful, there must have been a trial by a competent court where there was either a conviction or acquittal and not a mere discharge
NOTE: In some countries like the USA, Mexico, Canada, Israel, India etc. there is a “Double jeopardy clause”.