An industrial tribunal member may be challenged :
1° When he has a personal interest in the dispute, the mere fact of being affiliated to a trade union organisation not constituting such a personal interest;
2° If he is the spouse, partner in a civil solidarity pact, cohabitee, parent or relative up to and including the degree of first cousin of one of the parties;
3° If, in the year preceding the challenge, there has been legal, criminal or civil proceedings between him and one of the parties or his spouse, partner in a civil solidarity pact, cohabitee or his parents or relatives in the direct line;
4° If he has given a written opinion in the case;
5° If he is the employer or employee of one of the parties involved.