When a counterclaim raises questions affecting the interests of third parties, the defendant may, and if required by the judicial authority shall, cause such parties to be summoned in as parties to such suit. (See General Statutes § 52-110 and annotations.)
Section 9-21.—Counterclaim; Third Parties
Current through August 12, 2025 (2026 Practice Book edition) · Last verified July 9, 2026
In one sentenceWhen a counterclaim in a Connecticut case affects the interests of people who aren't yet parties, the defendant may, and sometimes must, summon those third parties into the suit.
Full Text of Section 9-21
Amendment History
(P.B. 1978-1997, Sec. 102.)
Plain-English Summary
Section 9-21 deals with counterclaims that reach beyond the plaintiff and defendant already in the case. If a counterclaim raises questions that affect the interests of third parties, the defendant asserting it has the option to bring those third parties into the suit by having them summoned in. If the judicial authority requires it, that option becomes a duty — the defendant must cause the third parties to be summoned in.
Frequently Asked Questions
Can a defendant bring in outside parties to answer a counterclaim in Connecticut?
Yes, if the counterclaim raises questions affecting third parties' interests, the defendant may cause those parties to be summoned in as parties to the suit.
Is summoning in third parties for a counterclaim always optional?
No. While a defendant may choose to summon in affected third parties, the judicial authority can require it, and once required the defendant must do so.
How does this rule relate to citing in new parties generally?
Section 9-22 sets the procedural requirements for any motion to cite in or admit new parties, including those summoned in under a counterclaim.
Source & verification. The section text is reproduced verbatim from the
official Connecticut Practice Book (Conn. Practice Book § 9-21). Prescribed by the Judges of the Superior Court of Connecticut (Conn. Gen. Stat. Section 51-14). The plain-English summary is original and written by us. Last verified July 9, 2026. ·
Official source
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