Also known as:motion for leave to intervene · intervention · permissive intervention
Written by attorneys · grounded in primary & secondary sources — see below
A procedural mechanism by which a nonparty obtains court permission to join an existing lawsuit as a party. The motion must state the grounds for intervention and be accompanied by a pleading that sets out the claim or defense sought to be asserted.
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Cases
Statutes
Federal Rules
Model Codes
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Hornbooks
How it applies
Common Examples
6
Insurer Seeks Entry in Negligence Suit
After a delivery truck owned by Lone Peak Energy struck a pedestrian, the pedestrian sued the driver for negligence. The driver's insurer, Loyal Insurance, moved for leave to intervene to assert that an intervening criminal act by a third party constituted a superseding cause relieving the driver of liability. The court granted the motion because the insurer's interest in the superseding-cause determination could not be adequately protected by the existing parties.
State Agency Joins Federal Claim
Lumen Capital sued a federal agency in district court under federal law for regulatory violations. A state environmental agency moved for leave to intervene to add a related state-law claim arising from the same transaction. The court granted leave because the state claim formed part of the same case or controversy as the federal claim.
Bystander Seeks to Defend Victim
During an assault on Luke Latham by an armed assailant, bystander Lillian Locke used force to protect Latham. When Latham later sued Locke for battery in civil court, Locke moved for leave to intervene to assert that she reasonably believed her intervention was necessary to protect Latham. The court granted the motion because Locke's justification defense shared common questions with the original action.
Neighbor Joins Tort Action
Luis Lopez's negligent storage of chemicals caused a fire that spread to Lily Lopez's adjacent property. Lily sued Luis. A neighboring business, Landmark Realty, moved for leave to intervene to assert that the fire's spread was a normal consequence of Luis's conduct and therefore not a superseding cause. The court granted leave because Landmark's property damage claim shared common questions with the original action.
Victim Seeks to Join Assault Claim
Lorenzo Lugo raised a chair and advanced toward Lucas Lee during a meeting, causing Lee to fear imminent contact. Lee sued Lugo for assault. Another attendee, Lillian Locke, moved for leave to intervene to assert her own assault claim arising from the same incident. The court granted the motion because Locke's claim shared common questions of law and fact with the original action.
Third Party Enters Foreseeability Dispute
Lumen Capital's negligent maintenance of a storage tank increased the risk that an intervening storm would cause flooding damage to nearby properties. Affected owners sued Lumen. One owner, Luke Latham, moved for leave to intervene to argue that the storm's intervention was foreseeable and therefore not a superseding cause. The court granted leave because Latham's claim shared common questions with the original action.
Common questions
Frequently Asked
5
When does a court grant leave to intervene under Rule 24(b)?+
A court grants permissive intervention when the applicant's claim or defense shares a common question of law or fact with the main action and intervention will not unduly delay or prejudice the original parties. The motion must be timely and accompanied by a pleading stating the grounds and the claim or defense.
Supporting sources
Does supplemental jurisdiction extend to claims asserted by an intervenor?+
Yes. Section 1367(a) expressly provides that supplemental jurisdiction includes claims that involve the joinder or intervention of additional parties when those claims form part of the same case or controversy as the claims within the court's original jurisdiction.
Supporting sources
Can an insurer obtain leave to intervene in a tort suit against its insured?+
Yes. An insurer may seek leave to intervene when coverage or liability issues, such as the existence of a superseding cause, will affect its obligations. Courts commonly grant the motion when the insurer's interests cannot be adequately represented by the existing parties.
Supporting sources
What must a motion for leave to intervene contain?+
The motion must be served on the parties, state the grounds for intervention, and be accompanied by a pleading that sets out the claim or defense for which intervention is sought.
Supporting sources
Does intervention require the applicant to show inadequacy of representation by existing parties?+
No. That requirement applies to intervention as of right. For leave to intervene under Rule 24(b), the applicant need only show a common question of law or fact and that intervention will not cause undue delay or prejudice.
Supporting sources
Constitutional LawThe nature of judicial review · Organization and relationship of state and federal courts in a federal systemUBEIntermediate