Rule 4 Order I of Code of Civil Procedure 1908 "Court may give judgment for or against one or more of joint parties"
Judgment may be given without any amendment-
(a) for such one or more of the plaintiffs as may be found
to be entitled to relief, for such relief as he or they may
be entitled to;
(b) against such one or more of the defendants as may be
found to be liable, according to their respective
liabilities.
Rule 5 Order I of Code of Civil Procedure 1908 "Defendant need not be interested in all the relief claimed"
It shall not be necessary that every defendant shall be interested as to all the relief claimed in any suit against him.
Rule 6 Order I of Code of Civil Procedure 1908 "Joinder of parties liable on same contract"
The plaintiff may, at his option, join as parties to the same suit all or any of the persons severally, or jointly and severally, liable on any one contract, including parties to bills of exchange, hundis and promissory notes.
Rule 7 Order I of Code of Civil Procedure 1908 "When
plaintiff in doubt from whom redress is to be sought"
Where the plaintiff is in doubt as to the person from whom he is entitled to obtain redress, he may join two or more defendants in order that the question as to which of the defendants is liable, and to what extent, may be determined as between all parties.
Rule 8 Order I of Code of Civil Procedure 1908 "One person may sue or defend on behalf of all in same interest"
(1) Where there are numerous persons having the same
interest in one suit,-
(a) one or more of such persons may, with the permission of
the court, sue or be sued, or may defend such suit, on
behalf of, or for the benefit of, all persons so interested;
(b) the court may direct that one or more of such persons
may sue or be sued, or may defend such suit, on behalf of,
or for the benefit of, all persons so interested.
(2) The court shall, in every case where a permission or
direction is given under sub-rule (1), at the plaintiff's
expense, give notice of the institution of the suit to all
persons so interested, either by personal service, or,
where, by reason of the number of persons or any other
cause, such service is not reasonably practicable, by public
advertisement, as the court in each case may direct.
(3) Any person on whose behalf, or for whose benefit, a suit
is instituted, or defended, under sub-rule (1), may apply to
the court to be made a party to such suit.
(4) No part of the claim in any such suit shall be abandoned
under sub-rule (1), and no such suit shall be withdrawn
under sub-rule (3) of rule 1 of Order XXIII, and no
agreement, compromise or satisfaction shall be recorded in
any such suit under rule 3 of that Order, unless the court
has given, at the plaintiff's expenses notice to all persons
so interested in the manner specified in sub-rule (2).
(5) Where any person suing or defending in any such suit
does not proceed with due diligence in the suit or defence,
the court may substitute in his place any other person
having the same interest in the suit.
(6) A decree passed in a suit under this rule shall be
binding on all persons on whose behalf, or for whose
benefit, the suit is instituted, or defended, as the case
may be.
Explanation: For the purpose of determining whether the
persons who sue or are sued, or defend, have the same
interest in one suit, it is not necessary to establish that
such persons have the same cause of action as the persons on
whose behalf, or for whose benefit, they sue or are sued, or
defend the suit, as the case may be.
Rule 8A Order I of Code of Civil Procedure 1908 "Power of court to permit a person or body of persons to present opinion or to take part in the proceedings"
While trying a suit, the court may, if satisfied that a person or body of persons is interested in any question of law which is directly and substantially in issue in the suit and that it is necessary in the public interest to allow that person or body of persons to present his or its opinion that question of law, permit that person or body of persons to present such opinion and to take such part in the proceedings of the suit as the court may specify.