That jurors should be impartial is of the very essence of a fair trial by jury. If they have already taken part in the trial of other persons implicated in the offense of which the defendant is charged, they have almost necessarily received an impression either for or against him. When they are challenged because of the fact that they were jurors in the previous hearing, the judge of the county court is required by the Penal Code, § 757, to test their impartiality. The challenge of itself raised the issue, and it was error not to frame appropriate questions to be put them on their voir dire, and hear testimony as to whether the case under investigation involved matters on which they had previously passed. Compare Wells v. State, 102 Ga. 658; Brown v. State, 104 Ga. 736. Judgment reversed.
All the Justices concur.