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The persons who are directly involved or interested in any act, affair, contract, transaction, or legal proceeding; opposing litigants.

Persons who enter into a contract or other transactions are considered parties to the agreement. When a dispute results in litigation, the litigants are called parties to the lawsuit. U.S. law has developed principles that govern the rights and duties of parties. In addition, principles such as the standing doctrine determine whether a person is a rightful party to a lawsuit. Also, additional parties may be added to legal proceedings once litigation has begun.

Parties in Lawsuits

In court proceedings, the parties have common designations. In a civil lawsuit, the person who files the lawsuit is called the plaintiff, and the person being sued is called the defendant. In criminal proceedings, one party is the government, called the state, commonwealth, or the people of the United States, and the other party is the defendant. If a case is appealed, the person who files the appeal is called the appellant, and the other side is called either the respondent or the appellee. Numerous variations on these basic designations exist, depending on the court and its jurisdiction. Assigning party designations allows the legal system and its observers to quickly determine the basic status of each party to a lawsuit.

Parties as Adversaries

The U.S. legal system is based on the adversarial process, which requires parties to a legal proceeding to contend against each other. From this contest of competing interests, the issues are presented to the court and fully argued. In the end, one of the parties will obtain a favorable result.

For the adversary process to fulfill its mission of producing justice, it is vital that the issues at stake be argued by persons who have a genuine interest in them. Under the old rules of Common-Law Pleading, which used to regulate who could bring a lawsuit, only a person who actually held title to disputed property could be a party in a lawsuit concerning the property. This technicality sometimes prevented a person who had the most to gain or lose on the issue from becoming a party and presenting his or her case. This rule has now been replaced by laws requiring every action to be prosecuted by the real party in interest. This is most important when one person is managing an asset for the benefit of another. For example, administrators of a deceased person's estate can sue to protect the estate's interests without having to join the beneficiaries of the estate as parties. This modern rule sharpens the issues so that the decision in a case puts a controversy to rest for all the parties involved.

The U.S. Supreme Court has developed the standing doctrine to determine whether the litigants in a federal civil proceeding are the appropriate parties to raise the legal questions in the case. The Court has developed an elaborate body of principles defining the nature and contours of standing. In general, to have standing a party must have a personal stake in the outcome of the case. A plaintiff must have suffered some direct and substantial injury or be likely to suffer such an injury if a particular wrong is not redressed. A defendant must be the party responsible for perpetrating the alleged legal wrong.

A person has standing to challenge a law or policy on constitutional grounds if he can show that the enforcement of the law or implementation of the policy infringes on an individual constitutional right. On the other hand, in most cases a taxpayer does not have standing to challenge policies or programs he is forced to financially support.

Legal Entities that Can Be Parties

Only an actual legal entity may initiate a lawsuit. A natural person is a legal entity, for example, and any number of people can be parties on either side of a lawsuit. A corporation is endowed by its charter with existence as a separate legal entity. A business partnership is usually not considered a legal entity, but generally it can sue or be sued in the partnership name or in the names of the individual partners.

Many states permit lawsuits under a common name. This arrangement allows a business to be sued in the commonly used business name if it is clear who the owner or owners are. A lawsuit against Family Dry Cleaners, for example, may entitle the plaintiff to collect a judgment out of the value of the business property. The plaintiff will not be able to touch property that belongs to the owner or owners personally, however, unless they have also been named defendants in the action.

When a group of persons wishes to start a lawsuit, the group has several options. If, for example, a group of residential property owners wants to contest the construction of a toxic waste disposal site in its community, it can file a lawsuit listing each property owner as a plaintiff. The group could also select an association name that the court accepts (Citizens Against Toxic Waste) to represent those individuals. A more expensive alternative would be to incorporate the group and file the suit under the corporation's name.

The Class Action provides another option for bringing parties into a large-scale civil lawsuit. In a class action lawsuit, thousands and even millions of persons can be parties. To obtain a class action designation, the plaintiffs must convince the court that many persons possess similar interests in the subject matter of the lawsuit and that the plaintiffs can act on the group's behalf without specifically identifying every individual member of the group as a party to the litigation. The class action lawsuit can be an economical method of resolving civil claims that involve large numbers of persons with common interests, especially when the amount of each individual claim is too small to warrant independent legal actions by the claimants.

The Capacity to Sue or Be Sued

A person must have the requisite legal capacity to be a party to a lawsuit. Some people are considered non sui juris: they do not possess full civil and social rights under the law. A child is non sui juris because the law seeks to protect the child from his or her improvidence until the child reaches the age of majority. A child who has not reached the age of majority has a legal disability. Others who suffer a similar legal disability include mentally ill persons, mentally retarded persons, and persons who are judged mentally incompetent because of illness, age, or infirmity. Legal disability does not mean, however, that persons in these categories are removed from civil actions. The claims or defenses of a person who is non sui juris usually can be asserted by a legal representative, such as a parent, guardian, trustee, or executor.

Prisoners also have limited rights as parties to civil actions. They can appeal their convictions and bring Habeas Corpus petitions to challenge the validity of their incarceration. They can file prisoners' rights cases for a violation of their federally protected Civil Rights. Some states permit prisoners to defend themselves in an action that threatens them with Forfeiture of their property, but most states will not permit prisoners to start a civil lawsuit against any other party during the period of incarceration. Convicted felons or prisoners given life sentences may suffer what is called civil death, a total loss of rights, including the right to be a party in a lawsuit.

Joinder of Additional Parties

Usually a plaintiff decides when, where, and whom she or he wants to sue. In some cases a plaintiff may wish to join, or add, other parties after the start of the lawsuit. Proper parties and necessary or indispensable parties may be added while the action is pending.

A proper party is anyone who may be a party in the lawsuit. The Joinder, or addition, of a proper party in a pending lawsuit is entirely permissible. The court may allow the joinder of an additional party, but the lawsuit does not have to be dismissed if it does not. In some states anyone who has an interest in the subject of the controversy is a proper party in the lawsuit. Some courts encourage joinder of everyone who could be affected by the decision.

Under modern rules of procedure in many states and the federal courts, joinder is not encouraged to the point where a lawsuit becomes unwieldy or cluttered with unrelated parties and claims. Generally, joinder is approved where the claims of the persons sought to be joined arose out of the same transaction or event as the claims of the existing parties, so that all the claims may be settled by answering the same questions of law or fact. The decision to join additional parties is within the discretion of the court. Courts are careful not to exclude parties with an interest in a lawsuit because a failure to join those parties might lead to a series of lawsuits with inconsistent verdicts. That could ultimately leave a deserving plaintiff without a remedy or force a defendant to pay a certain claim more than once.

Whether a person is potentially necessary or indispensable to an action depends on the character and extent of that person's interest in the subject of the lawsuit. It is fair and equitable to require any person who has an interest that can be affected by the lawsuit to be joined as a party. A person whose interest may be affected by the outcome of the case is considered necessary, and such a person should be joined if possible. A person whose interest is sure to be affected by the outcome of the lawsuit is considered an indispensable party, and the case cannot proceed without this person. The case must be dismissed, for example, if a person cannot be joined because he or she is beyond the jurisdiction of the court. In deciding whether a person should be a party to a lawsuit, the courts carefully weigh the consequences of proceeding without the person and seek a remedy that will give relief to those who are actual parties without doing great harm to a necessary or indispensable party who is missing.

Federal courts abandoned this analysis and terminology relating to necessary and indispensable parties in 1966. The Federal Rules of Civil Procedure focus on factors affecting the overall balance of fairness to the parties and potential parties involved rather than on categories of parties. Once a federal court determines that someone absent from the proceedings has an interest that can be affected by the case, the court must order that person to be joined as a party if it is practical to do so. If not, the court must weigh the competing interests of the plaintiff who would like to keep the case in federal court, the defendant who might be exposed to multiple lawsuits on the same issue, and the absent person whose rights may be lost if he or she does not become a party. The court must also consider how best to avoid wasting judicial time and resources and whether the case before it is the most efficient way to resolve the controversy.


A defendant who feels that the plaintiff in a lawsuit should have sued someone else on the claim can bring that other person into the case. The procedure for doing this is called Impleader, and the additional party is called a third-party defendant. The original defendant who impleads a third-party defendant is called a third-party plaintiff, but he or she continues to be a defendant in relation to the plaintiff.

For example, a restaurant patron who becomes ill after eating a ham dinner can sue the restaurant. The patron is the plaintiff, and the restaurant is the defendant. The restaurant may want to implead the meat-packing company that furnished the ham, if it believes that the meat was tainted before it was delivered to the restaurant. The restaurant cannot avoid being a defendant, but it can cover itself by impleading the meat packer and making that company a third-party defendant. If a jury finds that the ham was bad and that the patron is entitled to $10,000 damages, then the restaurant has an opportunity to show that its employees were not careless in preparing or serving the meat and that the restaurant should not be liable for the damages.

The decision to allow impleading of a third party is within the discretion of the court. The court also decides whether the third-party defendant may file claims against any of the other parties or whether the other parties may make additional claims against the third-party defendant. Permitting all parties to put forward all their claims in one action promotes efficient use of the courts, but a court will not permit additional parties or claims to complicate proceedings, delay resolution of the main controversy, or confuse a jury.


A person can volunteer to become a party in a lawsuit by a procedure called intervention. A person might wish to intervene in a lawsuit if he or she has an interest that will be affected by the outcome of the case and the person believes that this interest will not be adequately protected by the other parties.

A court decides whether to permit an intervening party by Balancing the interests of the person seeking to intervene with the additional burden imposed on the existing parties if the person is allowed to enter the lawsuit. The court considers whether the intervenor is raising the same issues already present in the case or whether the intervenor is seeking to inject new controversies into the case. The intervenor must demonstrate some practical effect of the outcome of the case on his or her rights or property. If a person is not allowed to intervene, the person is not bound by the judgment given in the case.

An intervenor must make the request to intervene in a motion to the court. Timing is important. If the case has already progressed beyond the preliminary stages, the court is likely to find that the intervenor's intrusion would prejudice the rights of the existing parties, which would be grounds for the court to deny the motion.

Further readings

Cohen, Alan G., et al, eds. 1992. The Living Law: A Guide to Modern Legal Research. Rochester, N.Y.: Lawyers Cooperative.

Kraut, Jayson, et al. 1983. American Jurisprudence. Rochester, N.Y.: Lawyers Cooperative.


Adversary System.

PARTIES, contracts. Those persons who engage themselves to do, or not to do the matters and things contained in an agreement.
     2. All persons generally can be parties to contracts, unless they labor under some disability.
     3. Consent being essential to all valid contracts, it follows that persons who want, first, understanding; or secondly, freedom to exercise their will, cannot be parties to contracts. Thirdly, persons who in consequence of their situation are incapable to enter into some particular contract. These will be separately considered.
     4.-Sec. 1. Those persons who want understanding, are idiots and lunatics; drunkards and infants,
     5.-1. The contracts of idiots and lunatics, are riot binding; as they are unable from mental infirmity, to form any accurate judgment of their actions; and consequently, cannot give a serious and sufficient consideration to any engagement. And although it was formerly a rule that the party could not stultify himself; 39 H. VI. 42; Newl. Contr. 19 1 Fonb. Eq. 46, 7; yet this rule has been so relaxed, that the defendant may now set up this defence. 3 Camp. 128; 2 Atk. 412; 1 Fonb. Eq. n. d.; and see Highm. on Lun. 111, 112; Long on Sales, 14; 3 Day's Rep. 90 Chit. on Contr. 29, 257, 8; 2 Str. 1104.
     6.-2. A person in a state of complete intoxication has no agreeing mind; Bull. N. P. 172; 3 Campb. 33; Sugd. Vend. 154 Stark. Rep. 126; and his contracts are therefore void, particularly if he has been made intoxicated by the other party. 1 Hen. & Munf. 69; 1 South. Rep. 361; 2 Hayw. 394; see Louis. Code, art. 1781; 1 Clarke's R. 408.
     7.-3. In general the contract of an infant, however fair and conducive to his interest it may be, is not binding on him, unless the supply of necessaries to him be the object of the agreement; Newl. Contr. 2; 1 Eq. Cas. Ab. 286; l Atk. 489; 3 Atk. 613; or unless he confirm the agreement after he shall be of full age. Bac. Abr. Infancy; I 3. But he may take advantage of contracts made with him, although the consideration were merely the infant's promise, as in an action on mutual promises to marry. Bull. N. P. 155; 2 Str. 907; 1 Marsh. (Ken.) Rep. 76; 2 M. & S. 205. See Stark. Ev. pt. iv. page 724; 1 Nott & McCord, 197; 6 Cranch, 226; Com. Dig. Infant; Bac. Abr. Infancy and Age; 9 Vin. Ab. 393, 4; Fonb. Eq. b. 1 c. 2; Sec. 4, note b; 3 Burr. 1794; 1 Mod. 25; Str. 937; Louis. Code, article 1778.
     8.-Sec. 2. Persons who have understanding, who, in law, have not freedom to exercise their will, are married women; and persons under duress.
     9.-1. A married woman has, in general, no power or capacity to contract during the coverture. Com. Dig. Baron & Feme, W; Pleader, 2 A 1. She has in legal contemplation no separate existence, her husband and herself being in law but one person. Litt. section 28; see Chitty on Cont. 39, 40. But a contract made with a married woman, and for her benefit, where she is the meritorious cause of action, as in the instance of an express promise to the wife, in consideration of her personal labor, as that she would cure a wound; Cro. Jac. 77; 2 Sid. 128; 2 Wils. 424; or of a bond or promissory note, payable on the face thereof to her, or to herself and husband, may be enforced by the husband and wife, though made during the coverture. 2 M. & S. 396, n. b.; 2 Bl. Rep. 1236; 1 H. Black. 108. A married woman has no original power or Authority by virtue of the marital tie, to bind her husband by any of her contracts. The liability of a husband on his wife's engagements rests on the idea that they were formed by his authority; and if his assent do not appear by express evidence or by proof of circumstances from which it may reasonably, be inferred, he is not liable. 1 Mod. 125; 3 B. & C. 631; see Chitty on Cont. 39 to 50.
    10.-2. Contracts may be avoided on account of duress. See that word, and also Poth. Obl. P. 1, c. 1, s. 1, art. 3, Sec. 2.
    11.-Sec. 3. Trustees, executors, administrators, guardians, and all other, persons who make a contract for and on behalf of others, cannot become, parties to such contract on their own. account; nor are they allowed in any case to purchase the trust estate for themselves. 1 Vern. 465; 2 Atk. 59; 10 Ves. 3; 9 Ves. 234; 12 Ves. 372, 3 Mer. Rep. 200; 6 Ves. 627; 8 Bro. P. C. 42 10 Ves. 381; 5 Ves. 707; 13 Ves. 156; 1 Pet. C. C. R. 373; 3 Binn. 54; 2 Whart. 53; 7 Watts, 387; 13 S. & R, 210; 5 Watts, 304; 2 Bro. C. C. 400; White's L. C. in Eq. *104-117; 9 Paige, 238, 241, 650, 663; 1 Sandf. R. 251, 256; 3 Sandf. R. 61; 2 John. Ch. R. 252; 4 How. S. C. 503; 2 Whart. 53, 63; l5 Pick. 24, 31. As to the transactions between attorneys and others in relation to client's property, see 2 Ves. jr. 201; 1 Madd. Ch. 114; 15 Ves. 42; 1 Ves. 379; 2 Ves. 259. The contracts of alien enemies may in, general be avoided, except when made under the license of the government, either express or implied. 1 Kent, Com. 104. See 15 John. 6; Dougl. 641. As to the persons who make contracts in equity, see Newl. Cont. c. 1, pp. l to 33.