Definition
The improper joining of parties or causes of action in a single lawsuit. Misjoinder occurs in two distinct ways:
1. Misjoinder of parties. The inclusion of a plaintiff or defendant who should not be joined in the action — either because the party lacks a legally sufficient connection to the claims at issue, or because the procedural rules governing permissive or compulsory joinder are not satisfied.
2. Misjoinder of causes of action. The combining in one proceeding of multiple claims that the law does not permit to be tried together — either because the claims are legally incompatible, arise from distinct substantive rights, or fail to meet the standards for permissive joinder under applicable procedure rules.
Misjoinder is distinct from nonjoinder, which is the failure to include a party who should have been joined. Both are procedural defects, but they arise from opposite errors.
Common Language
Modern common usage (Wiktionary): "An incorrect union of parties or of causes of action in a procedure in court."
Historical common usage (Webster's 1913): "An incorrect union of parties or of causes of action in a procedure, criminal or civil."
The common and legal definitions are unusually close here — this is a term that crossed from legal jargon into general reference dictionaries largely intact. The meaningful gap, however, is one of consequence: everyday usage treats misjoinder as a simple error, while legal usage attaches specific procedural remedies and historically differentiated sharply between misjoinder of parties (with varying consequences depending on plaintiff or defendant) and misjoinder of causes of action (which could be fatal to a pleading). The word alone does not convey which type of misjoinder is at issue or what follows from it.
Common Confusion
Misjoinder is frequently confused with nonjoinder. Misjoinder means too many or the wrong parties have been joined; nonjoinder means a required or necessary party has been omitted. The remedies differ. Under modern procedure, misjoinder is generally not grounds for dismissal — courts may drop the improperly joined party and proceed. Nonjoinder of an indispensable party, by contrast, can require dismissal if the party cannot be added. Researchers reading older sources must be alert: pre-code pleading treated misjoinder as far more consequential, particularly the misjoinder of defendants in contract actions, which was treated as fatal rather than curable.
Why It Matters in Research
The stakes of misjoinder changed dramatically with the shift from common law pleading to code pleading and then to modern rules-based procedure. In the older common law system, misjoinder — particularly of defendants in a contract action — was often fatal to the suit. Rapalje & Lawrence's entry reflects this clearly: misjoinder of defendants in contract was fatal; misjoinder of plaintiffs led only to increased costs. That asymmetry disappears almost entirely under modern federal and most state procedural rules, where misjoinder is treated as a curable defect, not a ground for dismissal.
Researchers working in pre-twentieth-century materials should look closely at which type of misjoinder is alleged (parties vs. causes of action), which side of the case the defect falls on (plaintiff vs. defendant), and whether the action sounds in contract or tort. The answers controlled the outcome under historical doctrine and will not map neatly onto modern procedure.
In modern federal practice, Federal Rule of Civil Procedure 20 governs permissive joinder of parties and Rule 18 governs joinder of claims. Rule 21 specifically addresses misjoinder, confirming it is not grounds for dismissal. Criminal misjoinder has its own track under Federal Rule of Criminal Procedure 8, which governs joinder of offenses and defendants, and Rule 14, which governs relief from prejudicial joinder. The civil and criminal doctrines are related but not identical, and corpus research should treat them separately.
Equity practice had its own version of this problem. Bouvier notes that in equity, misjoinder referred to the joinder of different and distinct claims against one defendant in one proceeding — a context with its own remedial structure that does not translate directly into either common law or modern rules-based analysis.
England's Judicature Acts of the 1870s substantially relaxed the old misjoinder rules, and Bouvier flags this transition explicitly. Researchers working in comparative or English legal history will find a meaningful doctrinal break at that point.
Historical Dictionary Support
The historical sources converge on the basic two-part structure: misjoinder of parties and misjoinder of causes of action. Burrill and Bouvier both define it cleanly in those terms, with Bouvier providing the most granular treatment, including the equity/law distinction and the shift introduced by English procedural reform.
Black's first edition gives the standard short definition without elaborating on consequences. Black's second edition redirects entirely to JOINDER, reflecting the editorial choice to consolidate procedural joinder doctrine under a single umbrella. Anderson takes the same approach. This is a meaningful signal for researchers: in the later Black's editions, the full doctrine is folded into the parent entry, which means keyword searches on MISJOINDER alone in index-based sources may miss substantial relevant content.
Rapalje & Lawrence provides the most useful historical detail of the shelf sources, distinguishing the pre-Judicature Act English rules on a plaintiff/defendant and contract/tort axis. The entry as excerpted in the source material cuts off mid-sentence, suggesting additional content on tort misjoinder that the historical record would supply.
One notable gap in the historical sources: none of them addresses criminal misjoinder as a developed doctrine. The Webster's 1913 definition acknowledges criminal procedure in passing ("criminal or civil"), but the legal dictionaries are almost entirely civil in orientation. Criminal misjoinder doctrine — the improper joinder of offenses or co-defendants — has its own substantial body of law that post-dates or runs parallel to the civil doctrine covered in these sources.
Jurisdictional Note
In federal court, misjoinder is governed by the Federal Rules of Civil Procedure and is explicitly non-fatal. State courts vary: most modern code states follow a similar approach, but some retain stricter standards for joinder of causes of action, particularly where claims arise under different bodies of substantive law. Criminal misjoinder doctrine varies at the state level in ways that can significantly affect severance motions and prejudice analysis.