Particular causes of challenge are of two kinds:
1. A bias which, when the existence of the facts is ascertained, in judgment of law disqualifies the juror, and which is known in this title as implied bias; and 2. The existence of a state of mind on the part of the juror, with reference to the case or to either party, which satisfies the court, in the exercise of a sound discretion, that the juror cannot try the issue impartially without prejudice to the substantial rights of the party challenging, and which is known in this title as actual bias.