A local government is not liable under Section 1983 simply because it employs someone who committed a constitutional violation. There is no vicarious or respondeat-superior liability for municipalities in this context. Instead, a plaintiff must show that the violation was caused by the municipality's own policy, custom, or decision -- that the entity itself, not just its employee, is the wrongdoer.

This makes Monell liability a fundamentally different inquiry from claims against individual officials. Qualified immunity protects individuals from personal liability and has no application to a municipality, but that does not make municipal liability easier to establish -- it simply substitutes a different, independently demanding element: proof that an official policy or custom was the moving force behind the violation.

Courts generally recognize several routes: an explicit, formally adopted policy that itself caused the violation; a widespread practice or custom, not formally adopted but so persistent and well settled that it represents the entity's effective policy; a single decision made by an official with final policymaking authority for the matter at issue; and a failure to train or supervise employees that amounts to deliberate indifference to the rights of the people the employees deal with. Some jurisdictions also recognize ratification, where a policymaker knowingly approves a subordinate's unconstitutional conduct and its basis.

Monell liability is a direct claim against the entity for its own policy-level conduct, not a claim that imputes an employee's misconduct to the employer -- that distinguishes it sharply from ordinary vicarious liability, which Section 1983 does not permit against municipalities. It is equally distinct from qualified immunity: immunity is a personal defense available only to individuals sued for their own discretionary conduct, and a municipality has no comparable immunity to assert. A plaintiff can therefore lose against the individual officer on immunity grounds while still pursuing -- or losing -- a separate Monell theory against the entity, because the two claims turn on entirely different elements.

Plaintiffs build the policy-or-custom element with formal policy documents, statistical patterns of similar incidents, internal reports, training materials, and evidence identifying the specific official who held final policymaking authority. Defendants attack by characterizing the incident as an isolated, non-representative event, disputing that the relevant decision-maker held final policymaking authority, or disputing the causal link between the policy and the specific injury.

Because Monell liability turns on an element entirely separate from the individual officer's conduct, it is best modeled as an independent claim path alongside -- not nested inside -- any claim against the individual official. In Juricratic terms, a matter involving both an individual defendant and a municipal defendant can carry two linked but distinct claim paths, each with its own dials (constitutional violation and clearly-established precedent for the officer; policy-or-custom strength and causation for the entity), so the combined exposure across both defendants can be war-gamed together without collapsing the two very different proof burdens into one.