(3) If it appears, at the trial of an issue on a plea of autrefois acquit or autrefois convict to an indictment for murder or manslaughter, that the first trial was for an offence committed against the person now alleged to have been killed, and the death of the person is now alleged to have been caused by the offence previously charged, but that the death happened after the trial at which the accused was acquitted or convicted, as the case may be, then, if it appears on the first trial not the accused, if convicted, might have been sentenced to imprisonment with hard labour for 3 years or more, the Court shall direct that the accused be discharged from the indictment before it, or direct that the accused pleads over.